Material guiding structure in a printing material container

ABSTRACT

Examples of the present disclosure relate to a base for a printing material container. The base has a channel structure defining an opening of the base, an axis of the channel structure defining an axial direction. The base also has a material-guiding structure, formed around the opening, having a helical lower surface that extends from the channel structure in the axial direction. An upper surface of the material-guiding structure is formed by a lower surface of the base and the helical lower surface meets the lower surface of the base at a curved side wall that extends radially from the channel structure to an annular portion of the base.

BACKGROUND

Certain printing systems make use of a printing material during aprinting process. For example, a two-dimensional printing system may usea container to store toner and a three-dimensional printing system mayuse a container to store a build material. In both cases, the printingmaterial is conveyed from the container to the printing system to allowprinting. In a two-dimensional printing system, the toner may be usedfor image formation on a print medium, such as a sheet of paper. In athree-dimensional printing system, the build material may be used toform a three-dimensional object, such as by fusing particles of buildmaterial in layers, whereby the object is generated on a layer-by-layerbasis.

BRIEF DESCRIPTION OF THE DRAWINGS

Various example features will be apparent from the detailed descriptionwhich follows, taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a schematic illustration showing a number of views of anexample container;

FIG. 2 is a schematic illustration showing a container in use within aprinting system according to an example;

FIG. 3 is a schematic illustration showing a number of stages that areinvolved when inserting a container into a supply station;

FIG. 4 is a schematic illustration showing rotation of a container intwo opposing directions according to an example;

FIG. 5 is a schematic illustration showing views of an example supplystation comprising hoppers;

FIG. 6 is a flow chart showing a method for conveying printing materialaccording to an example;

FIGS. 7A to 7E are schematic diagrams showing example aspects of achannel structure and a valve structure for a container;

FIG. 8 is a flow chart showing a method for conveying printing materialaccording to an example;

FIGS. 9A to 9E are schematic diagrams showing configurations of achannel structure for an example container;

FIG. 9F to 9G are schematic diagrams showing an example capconfiguration for a container;

FIG. 10 is a flow chart showing a method of sealing a containeraccording to an example;

FIG. 11 is a schematic diagram showing two views of an example containerformed from two independent portions;

FIGS. 12A to 12F are schematic diagrams showing aspects of amaterial-guiding structure according to examples;

FIG. 13 is a flow chart showing a method for conveying printing materialaccording to an example;

FIG. 14 is a schematic diagram showing an external view of an examplecontainer;

FIG. 15 is a schematic diagram showing a mold for manufacturing theexample container of FIG. 14;

FIGS. 16A-C are schematic diagrams showing views of an example containerhaving a handle and a planar portion;

FIG. 17 is a schematic diagram showing a mold for manufacturing theexample container of FIGS. 16A-C;

FIGS. 18A and 18B are schematic diagrams showing a raised planar portionin an example container;

FIG. 19 is a schematic diagram showing a mold for manufacturing theexample container of FIGS. 18A-B;

FIGS. 20A and 20B are flow charts showing example methods of conveying aprinting material;

FIGS. 21A to 21D are schematic diagrams illustrating a process ofjoining portions of a container according to an example;

FIG. 22 is a flow chart showing a method of manufacturing a containeraccording to an example; and

FIG. 23 is an exploded view of a further example container.

DETAILED DESCRIPTION

Certain examples described herein relate to a container to storeprinting material for use in a printing system. Example containers asdescribed herein may be used to supply a printing material totwo-dimensional printing systems, e.g. as developer or toner particles,or to supply a build material to three-dimensional printing systems. Theprinting material may be a powder or powder-like material.

Certain examples described herein provide a rotatable container withcomponents to allow efficient conveyance of printing material to aprinting system. By using a rotatable container, space may be moreefficiently used within a printing system, for example the container maybe horizontally aligned as compared to gravity feed supply systems thatmay require a long vertical hopper.

Certain examples described herein provide material-conveying and/ormaterial-guiding structures that allow printing material to be dispensedfrom and/or refilled to a container at a controlled rate. For example,material-conveying and/or material-guiding structures as describedherein may enable printing material to be supplied to a printing systemfrom a container at a rate that depends on a rotational speed of thecontainer.

Certain examples described herein provide a container with components toenable rotation in two opposing directions, e.g. clockwise andanti-clockwise. Rotation in a first of the two directions may allow forsupply of printing material from the container to the printing system,whereas rotation in a second of the two directions may allow for fillingof the container with printing material from the printing system.

For example, certain printing processes may result in an accumulation ofused printing material in the printing system. In a three-dimensionalprinting system this may comprise non-solidified, or unfused, buildmaterial that is removed from around a printed three-dimensional object.In a two-dimensional printing system, this may comprise toner that doesto contribute to an image that is cleaned from a photoconductive surfaceduring print. It may be useful to remove this excess used material fromthe printing system in a clean and tidy way. This may be achieved usingcertain example containers as described herein. In one case, excessprinting material may be loaded back into a container by feedingmaterial to a material-conveying member arranged within an opening ofthe container while the container is rotating in a second “fill” or“intake” direction. If it is desired to increase a rate of excess powderremoval, a rate of rotation may be increased. At a predefined rate,rotation cause compaction of the printing material and may thus increasethe capacity of the container. If it is desired to remove printingmaterial from the printing system for reuse at a later time, thecontainer can be filled to a normal level by rotating at a slower rate.In other examples, the container may be configured such that rotation inone of the two directions conveys printing material whereas rotation inthe other of the two directions does not convey printing material, e.g.the container may be configured to be filled with but not supplyprinting material.

Certain examples described herein provide a container that may becheaply and efficiently manufactured. The container allows printingmaterial to be easily delivered to a printing system, and certaincomponents described herein allow for easy storage and handling. Toreduce and/or reverse possible effects of consolidation, compaction andsegregation during delivery, the container may be rotated in the second“fill” or “intake” direction to re-aerate and re-mix (i.e. “refresh”)the printing material. “Mixing” in this sense relates to mixing of theprinting material within the container, e.g. either with itself or withair. This enables printing material to be supplied to the printingsystem with expected and/or original properties and flow behaviors. Forexample, following shipping and after installation, a container may bequickly “refreshed” via a short rotation in a direction opposite to adirection for supply of the printing material. In certain cases, e.g.during filling of the container, a volume of air may be provided in thecontainer to allow later refresh by tumbling.

FIG. 1 shows multiple views of a container for printing materialaccording to an example. The views show schematically certain aspects ofan example container to provide a context to the following examples. Itshould be noted that an actual container configuration may vary incertain aspects from that shown in FIG. 1. For example, shapes ofcertain aspects and/or relative dimensions may vary according toimplementations. A first view 101 shows a top of the container 100. Asecond view 102 shows a side cross section of the container 100. A thirdview 103 shows a bottom of the container 100. A fourth view 104 shows anexternal side of the container 100.

The container of FIG. 1 comprises a hollow chamber 110 formed by aninner wall 120. The chamber 110 has an open end 130 and a closed end140. The open end 130 has an opening 135 through which printing materialmay be conveyed to and/or from the chamber 110. The opening 135 isformed within a channel structure 150 that surrounds the opening 135.The channel structure 150 is a portion of the open end 130 in which theopening 135 is formed. The closed end 140 prevents printing materialfrom escaping the chamber 110. The inner wall 120, open end 130, closedend 140 and channel structure 150 may be formed from a single componentor may be formed by a number of joined independent components. Forexample, in one case, the container 100 may comprise a single moldedarticle. In another case, the container 100 may comprise a moldedchamber and a molded upper portion that are joined together, e.g. bywelding. In yet another case, the container 100 may comprise a moldedchamber and separate upper and lower portions that are joined together.In the latter two cases, the channel structure 150 may form part of anupper portion that is joined to a molded chamber.

The container 100 of FIG. 1 has a generally cylindrical form. Forexample, this may be seen in the first and third views 101, 103, wherethe container 100 has a circular cross-section. The cross-section of animplementation may vary from a precise circle, e.g. may be generallycurved but with projections and indentations. In the second and fourthviews 102, 104 it may be seen how, in this example, the container 100 isan elongate cylinder that extends along an axis 155. By way of thesefeatures the container 100 is rotatable, e.g. about axis 155. Thecontainer 100 may be defined with a diameter D and a length L. Incertain implementations, D may be in a range of 150 to 200 mm and L maybe in a range of 400 to 500 mm. In other examples the container 100 maybe provided in a variety of dimensions. In other examples, the container100 may comprise a different shape and/or cross-section yet still berotatable about a central axis. Additionally, as described withreference to certain examples later below, the cross section of thecontainer 100 may not be a perfect circle, but may comprise indentationsand/or projections. In FIG. 1, the opening 135 is co-axial with thechamber 110, i.e. the center of the opening 135 and the center of thechamber 110 both lie upon the axis 155.

The container 100 of FIG. 1 also has an outer wall 160. The inner wall120 and the outer wall 160 are respectively inner and outer surfaces ofa side wall of the container 100. In other examples, the inner wall 120and the outer wall 160 may form separate walls of the container 100,e.g. the container 100 may comprise a gap or cavity between the innerand outer walls 120, 160. The container 100 may be rotated in use. Inone case, the container 100 may be mounted within a rotatable mounting,such as a cage or the like. By rotating the cage, the container 100 isrotated. In other cases, the container 100 may be rotated by applying aforce to the outer wall 160, e.g. via one or more rollers mounted aroundthe outer wall 160. In one case, one or more of the open end 130 and theclosed end 140 may comprise mounting portions for mounting the container100 within a material supply station.

FIG. 2 shows a printing system 200 according to an example, wherein theprinting system 200 is adapted to use the container 100 of FIG. 1. Theprinting system 200 comprises a chassis 210 that encloses a materialsupply station 220 and a printing station 230. In other examples, thematerial supply station 220 and/or container 100 may be located in adifferent chassis to the printing station 230. In use, the materialsupply station 220 supplies printing material to the printing station230. In certain cases, the printing station 230 may also supply excessor used printing material back to the material supply station 220 (or aseparate reuse station having similar functionality). In certain cases,printing material may be supplied from the printing system 200 to thecontainer 100 before it is sent to the printing station 230, e.g. unusedprinting material may be supplied to the container 100 from internalstorage to swap a printing material type, e.g. to change colors or buildmaterial type.

If the printing system 200 comprises a two-dimensional printing system,the printing station 230 may comprise an image forming unit including aphotoconductor drum, a developer unit and a cleaning unit. The developerunit may deposit toner material supplied from the material supplystation 220 onto the photoconductive drum following charging and imageexposure, i.e. “develop a toner image”. The toner image may betransferred to a print medium, such as paper, to form a printed output.Excess toner may be removed from the photoconductor drum by the cleaningunit.

If the printing system 200 comprises a three-dimensional printingsystem, the printing station 230 may comprise a material feed unit, aplaten and a selective solidification unit. The material feed unit mayreceive build material from the material supply station 220 to createlayers of build material upon the platen. The solidification unit maythen act to selectively solidify portions of each layer of buildmaterial. The platen may be moved vertically to enable successive layersof build material to be formed. By repeating this processthree-dimensional objects of almost any shape may be generated from adigital three-dimensional model.

If the printing system 200 comprises a three-dimensional printingsystem, the printing station 230 may implement an additive manufacturingprocess. In these processes, three-dimensional objects are generated ona layer-by-layer basis under computer control. The printing station 230may implement one or more of additive manufacturing technologies to forma three-dimensional object from supplied powdered build material. Suchtechniques include, for example, selectively melting semi-crystallinethermoplastic powdered build materials, and/or selective electron-beammelting of metal powder build material.

In some three-dimensional printing system examples, solidification of abuild material is enabled using a liquid binding agent, such as anadhesive. This liquid agent may be applied using a moveable print headlocated above the platen referenced above. In certain examples,solidification may be enabled by temporary application of energy to thebuild material, for example using a focused laser beam. In certainexamples, liquid fusing agents are applied to build material, wherein afusing agent is a material that, when a suitable amount of energy isapplied to a combination of build material and fuse agent, causes thebuild material to heat up, to melt, fuse and solidify. Other agents mayalso be used, e.g. agents that inhibit or modify a level of fusing whenselectively deposited in certain areas. Fusing of build material may beperformed using thermal or non-thermal methods. Non-thermal fusingtechniques may include techniques such as binder jetting. A liquid agentmay be applied using a thermal or piezoelectric printhead.

The printing system 200 may receive a definition of an image or objectto be printed in digital form. In a two-dimensional case, the image maybe decomposed into multiple color separations for printing. In thiscase, the material supply station 220 may comprise toner of differentcolors from different containers 100. There may be a common materialsupply station or different material supply stations for each color. Ina three-dimensional case, a digital representation may be virtuallysliced into slices by computer software or may be provided in pre-slicedformat. Each slice represents a cross-section of the desired object.

In the example of FIG. 2, the container 100 is mounted horizontally,i.e. wherein the axis 155 is substantially perpendicular to agravitational axis (e.g. the vertical). In other cases, the container100 may be mounted at an angle to the horizontal, e.g. at an angle of upto 20-30 degrees. To supply printing material to the printing station230, the material supply station 220 is arranged to rotate the container100. This is explained in more detail with regard to FIGS. 3, 4 and 5below.

FIG. 3 shows schematically a number of stages in a process of coupling acontainer 100 to a material supply station 220. A first stage 301 showsa first point in time where a container is not mounted within thematerial supply station 220. A second stage 302 shows a second point intime where a container is inserted into the material supply station 220.A third stage 303 shows a third point in time where a container 100 ispresent within the material supply station 220. For each stage, aschematic side cross section of the material supply station 220 isshown. Certain features of the container 100 and the material supplystation 220 have been omitted in each stage to clearly show the processof insertion. For the first and third stages 301, 303, a front view ofthe material supply station 220 is also shown on the right hand side.Views 302 and 303 show a schematic cross section of the container 100.

In the example of FIG. 3, the material supply station 220 comprises amounting, or receiving interface, 310 and an intake 320. The intake 320may be seen as a component of the printing system that couples to thecontainer 100. The mounting 310 comprises an elongate passageway or cagethat is configured to receive the container 100. The mounting 310 maycomprise closed and/or open sections, e.g. may comprise an elongate tubewith a continuous inner surface and/or discrete supporting memberslocated around a volume of space where the container 100 is to belocated (e.g. as per a cage). In one case, the mounting 310 may comprisea guide surface along which a corresponding outer surface of thecontainer 100 (e.g. at least a portion of outer wall 160) may be guidedduring insertion. This guide surface may be located at a base of themounting 310. In certain examples, the mounting 310 may compriseretractable members, wherein the members are retracted during insertionof a container and are extended to grip a container when the containeris in place. The mounting 310 may be configured to fully receive thecontainer 100 within the material supply station 220 and/or chassis 210,or may be configured such that an end of the container 100 projects outfrom the material supply station 220 and/or chassis 210. Although notshown, the material supply station 220 and/or chassis 210 may comprise adoor that is opened to reveal the mounting 310 and that is closed duringnormal operation (e.g. with or without an inserted container 100). Inone case, the mounting 310 may be rotated to rotate the container 100,e.g. if the mounting comprises a cage that receives the container 100the cage may be rotated to rotate the container 100.

The intake 320 as shown in FIG. 3 comprises one or more components toreceive the channel structure 150 of the container 100 and thus to allowprinting material to be supplied to or extracted from the container viathe opening 135. The intake 320 may comprise one or more bearings, e.g.in an annular member that receives the channel structure 160. The intake320 may also comprise a mechanical coupling that attaches to thecontainer 100 to retain the container 100 in place. The mechanicalcoupling may attach to the channel structure 150 and/or outer wall 160,and/or a component of the container 100 as described in more detaillater below.

The second stage 302 shows that the container 100 is alignedhorizontally with the mounting 310, with the opening 135 facing theintake 320. The container 100 is then pushed into the mounting 310 fromthe front of the material supply station 220. The container 100 may beinserted by applying a force to the closed end 140 of the container 100.The container 100 may be inserted manually, via a robot actuator and/orvia a container transport system. The container 100 is inserted untilthe open end 130 of the container 100 reaches the intake 320. At thispoint, the channel structure 150 may form a sealed coupling with theintake 320. This is shown in the third stage 303.

The third stage 303 shows the container 100 in place within the mounting310. The channel structure 150 is accommodated within the intake 320. Inone example, the intake 320 may be configured to unseal the container100, e.g. via translation of a valve structure as described in moredetail below. Once the container 100 is in place printing material maybe extracted from the container 100, and/or printing material may besupplied to the container 100, through the opening 135 and the intake320. For example, the intake 320 may be coupled to a feed system thatprovides printing material to the printing station 230. This process maybe direct or indirect, e.g. printing material may be directly conveyedto and/or from the printing station 230, or may be conveyed to and/orfrom intermediate storage components within the printing system 200. Thefeed system may comprise one or more tubes, filters, pumps, blowers,separators and/or hoppers. The feed system may apply a pressuredifferential to facilitate powder extraction and/or to transportprinting material within the printing system.

FIG. 3 shows one example method of coupling a container 100 to amaterial supply station 220. Other methods and structures are possible.For example: the container 100 may be installed at an angle to thehorizontal or vertically; the material supply station 220 may provide anopening from above, a side or below instead of at the front; and/or thecontainer 100 may be rolled or slid into place.

FIG. 4 shows how printing material may be conveyed to and/or from aninstalled container 100 via rotation of the container 100. In thisexample, the container 100 is configured such that rotation of thecontainer 100 in a first direction conveys the printing material to theintake 320 and rotation of the rotatable chamber in a second directionconveys the printing material away from the intake 320. In particular,by rotating the rotatable chamber 110 of the container 100, printingmaterial may be supplied to and/or from the printing system 200 so as torespectively deplete and/or at least partially fill the volume of thechamber 110.

In a first stage 401 in FIG. 4, the container 100 is rotated in a firstdirection 410. The rotation may be applied by the material supplystation 220 or by an external agent. In the former case, a cage thatholds the container 100 may be rotated. Alternatively, in otherexamples, rollers positioned around the container 100 may apply a forceto the outer wall 160 to rotate the container 100 within the mounting310. In the latter case, a handle or grip may be provided at the closedend 140 of the container 100 to allow the container 100 to be rotated bya human or robot agent. In the first stage of FIG. 4, rotation isclockwise. However, depending on the container implementation, thedirection may be counter-clockwise in other examples. The left hand sideview of the first stage 401 shows printing material being supplied tothe material supply station 220 from the container 100 during therotation. Printing material may then be distributed to other componentsof the printing system 200 from the material supply station 220. In thefirst stage 401, printing material is depleted within the container 100during rotation.

In a second stage 402 in FIG. 4, the container 100 is rotated in asecond direction 420. Again, the rotation may be applied by the materialsupply station 220 or by an external agent. In the second stage of FIG.4, rotation is counter-clockwise (or anti-clockwise). However, dependingon the container implementation, the direction may be clockwise in otherexamples (i.e. the directions of the first and second stage may bereversed). The left hand side view of the second stage 402 showsprinting material being supplied from the material supply station 220 tothe container 100 during the rotation. In the second stage 402, thecontainer 100 is filled with printing material,

In certain cases, the container 100 may be configured such that eachcomplete rotation of the cylinder in the first direction conveys apredefined quantity of printing material to the material supply station220. For example, this may be achieved by providing and configuring amaterial-conveying member and/or a material-guiding structure asdescribed in more detail later below.

FIG. 5 shows a variation of the example of FIGS. 3 and 4. Two views areshown: a schematic side cross section 501 and a schematic front crosssection 502. In this variation two containers 505 and 510 are mountablewithin a print supply station 520 (based on material supply station220). For example, the first container 505 may provide unused or“virgin” powdered material and the second container 510 may be used tocollect or provide used powdered material. For example, in certain casesthe second container 510 may provide used printing material ifsufficient used printing material cannot be provided by the printingsystem itself (e.g. due to a print run just starting or the size orquality of objects that are being produced). Used printing material mayalso be supplied while switching from one printing material to another.As such, during a printing process, printing material 515 may besupplied to a printing station such as 220 by rotating the firstcontainer 505 in a first direction and used printing material resultingfrom the printing process may be supplied to the second container 510 byrotating the second container 510 in a second direction. It will beunderstood that this approach may be extended to more than twocontainers and that the directions, and supply/fill configuration, mayvary according to the implementation.

FIG. 5 also shows the use of two intermediate hoppers 540, 550 forprinting material. These may be used as buffers within the printingsystem 200. For example, a first intermediate hopper 540 may receiveprinting material 545 from the first container 505. The printingmaterial 545 may then be supplied to the printing station 230 from thefirst intermediate hopper 540. The second intermediate hopper 550 maythen receive printing material from the printing station 230. Thisprinting material may be temporarily stored before being used to fillthe second container 510 and/or to generate print output. Eachintermediate hopper 540, 550 may be coupled to a corresponding intakewithin the material supply station 520, for example by a feed systemcomprising components as referenced above.

FIG. 6 shows an example method 600 for conveying printing material to orfrom a container, e.g. to or from a component of a printing system. Forexample, this method may be applied to printing system 200 or anotherdifferent printing system. The component of the printing system maycomprise a material supply station such as material supply station 220,520 or the like. At block 610, a container (such as container 100) isrotated in a first direction to convey printing material from aninterior of the container, e.g. towards the component of thethree-dimensional printing system relative to the interior of thecontainer. For example, this is shown in the first stage 401 of FIG. 4.At block 620, the container is rotated in a second direction to conveyprinting material into the interior of the container, e.g. away from thecomponent of the printing system relative to the interior of thecontainer. For example, this is shown in the second stage 402 of FIG. 4.The first and second directions may be clockwise and counter-clockwiseor vice versa. Rotation in either direction may be applied independentlyin certain examples, e.g. a container may be emptied but not refilled orfilled but not emptied. For example, empty containers or container thatare filled with used printing material may be recycled.

In one case, a complete rotation of the cylinder in the first directionconveys a predefined quantity of printing material to the printingsystem. This may be referred to as a “dose” of printing material. Thismay be achieved when the container contains at least a predefinedquantity of printing material. As described elsewhere the printingmaterial may comprise a powder, e.g. be a powdered material.

In one case, block 610 may be performed for a predetermined timeinterval to supply a predefined quantity of printing material to theprinting system. This may be provided directly to a printing station orstored temporarily in an intermediate hopper. In this case, rotating thecontainer in the second direction may be performed at one or moreintervals during rotation of the container in the first direction to mixthe printing material during supply of the printing material to theprinting system. In this case, “mixing” is performed in relation to theprinting material within the container, as opposed to a mixing ofdifferent printing materials. This may be seen as “self” mixing, e.g.changing a configuration of material particles, and/or mixing with airwithin the container. For example, a first quantity of printing materialmay be supplied by rotating the container in the first direction. Oncethe first quantity has been supplied, rotation of the container in thefirst direction may cease, and rotation of the container in the seconddirection may be started to mix or “refresh” the printing material inthe container. The rotation in the second direction may be performed fora different length of time as compared to the rotation in the firstdirection. For example, the rotation in the second direction may beperformed for a shorter time period. The rotation in the seconddirection may also be performed at a different rate of rotation to therotation in the first direction. For example, the rotation in the seconddirection may be faster. For a container with a diameter of between 150and 200 mm and a length of between 400 and 500 mm, a rate of rotationmay be up to 2 Hz. The container may then be again rotated in the firstdirection to deliver newly refreshed printing material to the channelstructure, and thus to the printing system via an intake, at a rate thatdepends on the rotational speed. In one case, the container may berotated in the second direction when the container is first installed,i.e. before rotation in the first direction. This may enable printingmaterial to be “refreshed” following shipping, storage and handling.

Rotation in the second direction may also be performed after an image orobject has been printed, e.g. to supply unused printing material backinto the container. For supply of printing material to the container, arate of the rotation in the second direction may be configured toprovide a flow rate of 5 g/s into the container.

In the above case, rotating the container in the second direction maycomprise rotating the container at a predefined rate to compact apowdered printing material within the container during filling of thecontainer. For the example dimensions above, a predefined rate greateror equal to 2 Hz generates centrifuging motion that compacts printingmaterial within the container. This rate may be applied for around 10minutes to provide compaction. Compaction may be controlled bycontrolling a rate of rotation and a time of rotation. For example, asmaller centrifugal force applied for a longer time may have anequivalent effect to a larger centrifugal force applied for a shortertime. Compaction of printing material may increase a capacity of thecontainer, i.e. reduce the volume of a given quantity of powderedmaterial within the container to allow more powder to be stored ascompared to an uncompacted case. Compaction may not be desired if theprinting material is to be supplied again from the container (e.g. viarotation in the first direction). In certain cases, compaction may bereversed by varying the rotation parameters. In the present example,rotation at 1.2 Hz provides cascading motion of printing material withinthe container and rotation at 1.5 Hz provides cataracting motion. Theseforms of motion may reverse the effects of compaction by mixing theprinting material.

In one case, the component of the printing system comprises a materialsupply system and the method comprises, prior to rotating the containerin the first direction: inserting the container into the material supplysystem; and coupling an opening of the container to an intake of thematerial supply system. This, for example, is shown in FIG. 3. As shownin this Figure, the container may be aligned horizontally within thematerial supply system. In one case, coupling the opening of thecontainer to the intake of the material supply system comprisestranslating a valve structure within the opening to unseal thecontainer. This may also be performed independently of any coupling tounseal the container. The valve structure may be an auger valve. This isdescribed in more detail in later examples.

Example properties of the printing material will now be brieflydiscussed. The printing material may be a dry, or substantially dry,powder or powder-like material. In other examples, the printing materialmay comprise a liquid-type build material such as a viscous liquid,paste, or gel, In a three-dimensional printing example, a printingmaterial may have an average volume-based cross-sectional particlediameter size of between any one of the following: approximately 5 andapproximately 400 microns, between approximately 10 and approximately200 microns, between approximately 15 and approximately 120 microns orbetween approximately 20 and approximately 70 microns. Other examples ofsuitable, average volume-based particle diameter ranges includeapproximately 5 to approximately 70 microns, or approximately 5 toapproximately 35 microns. A volume-based particle size is the size of asphere that has the same volume as the printing particle. With “average”it is intended to explain that most of the volume-based particle sizesin the container are of the mentioned size or size range but that thecontainer may also contain particles of diameters outside of thementioned range. For example, the particle sizes may be chosen tofacilitate distributing printing material layers having thicknesses ofbetween approximately 10 and approximately 500 microns, or betweenapproximately 10 and approximately 200 microns, or between approximately15 and approximately 150 microns. One example of an additivemanufacturing system may be pre-set to form powdered material layers ofapproximately 80 microns using build material containers that containpowder having average volume-based particle diameters of betweenapproximately 40 and approximately 60 microns. An additive manufacturingapparatus may also be configured or controlled to form powder layershaving different layer thicknesses.

In a three-dimensional printing (i.e. additive manufacturing) case, aprinting material for use in example containers described herein mayinclude at least one of polymers, crystalline plastics, semi-crystallineplastics, polyethylene (PE), polylactic acid (PLA), acrylonitrilebutadiene styrene (ABS), amorphous plastics, Polyvinyl Alcohol Plastic(PVA), Polyamide, thermo(setting) plastics, resins, transparent powders,colored powders, metal powder, ceramics powder such as for example,glass particles, and/or a combination of at least two of these or othermaterials, wherein such combination may include different particles eachof different materials, or different materials in a single compoundparticle. Examples of blended build materials include alumide, which mayinclude a blend of aluminum and polyimide, multi-color powder, andplastics/ceramics blends. Blended build material may comprise two ormore different respective average particle sizes. Printing material asused herein also covers build materials comprising fibers. These fibersmay for example be formed by cutting extruded fibers into short lengths.For example, a fibre length may be selected to allow effective spreadingof the build material onto a platen or build platform. For example, thelength may be approximately equal to the diameter of the fibers.

Keeping with a three-dimensional printing example, a brief furtherexplanation of the notion of “unused” and “used” printing material willnow be provided. For example, containers as described herein may beinitially filled with unused printing material for supply to a printingsystem and/or may be filled with used printing material arising from aprinting process of the printing system.

A particular batch of printing material for use in an additivemanufacturing process may be fresh (e.g. “unused”) build material or“used” build material. Fresh build material should be considered to bebuild material which has not previously been used in a three-dimensionalprinting build job. For example, this may comprise build material thathas not been heated during a thermal process and/or build material thathas not received a chemical binder in a non-thermal process. An unopenedsupply of build material as supplied by a build material manufacturermay therefore contain fresh build material. By contrast, used buildmaterial is build material which has previously been supplied to athree-dimensional printing system for use in an additive manufacturingprocess but which has not been solidified during the process. Forexample, the used build material may be produced during athermal-fusing, three-dimensional printing operation, in which powderbuild material is heated to close to its melting temperature for aperiod of time which may be sufficient to cause material degradation ofthe powder. In this respect, it will be understood that not all of thebuild material supplied to a three-dimensional printing system for usein an additive manufacturing process may be used and/or incorporatedinto a three-dimensional printed article. At least some of thenon-solidified build material recovered during or after completion of athree-dimensional print job may be suitable for reuse in a subsequentadditive manufacturing process. Such build material may be stored, forexample in the containers described herein, for subsequent use, and maybe designated as ‘used’ build material.

Continuing the above example, the used build material may also be mixedwith fresh build material for subsequent printing processes. In theexample of FIG. 5, the first container 505 may comprise fresh buildmaterial that is mixed with used build material present within thesecond container 510. The mixing proportion may be variable, for examplebased on powder properties. Mixing may be performed externally orinternally, with reference to the containers. For example, mixing may beperformed using (or within) a feed system and/or one or moreintermediate hoppers, or used build material may be supplied to thecontainer for a first period and virgin build material supplied to thecontainer for a second period. In one case, an internal hopper may haveat least twice the capacity of a container. In one case, mixing may beperformed during use within a feed system based on pneumaticconveyancing, e.g. on printing material extracted from the containersand/or internal hoppers. The container may then be further rotated tomix the combination within the container. In one example, a mix of 80%used and 20% fresh build material may be used for objects for someapplications, with 100% fresh build material being used for objects forother applications.

In general, printing material containers may be used to supply recycledor reconditioned (e.g. used but unsolidified in a three-dimensionalcase) printing material in addition to, or instead of, fresh printingmaterial. In certain cases, printing material of varying qualities maybe supplied, e.g. different printing material containers may supplydifferent grades of printing material that each adhere to differentquality specifications. In some examples, used printing material may bereturned to a supplier.

Aspects of a rotatable container for storing a printing material for aprinting system, in particular relating to a channel and/or valvestructure for such a container, will now be described with reference toFIGS. 7A to 7E. These aspects relate to a material-conveying member thatmay be located within an opening of the container, e.g. opening 135 asshown in FIG. 1.

FIG. 7A shows schematically a rotatable container 701 for storing aprinting material for a printing system. The container 701 may be basedon container 100 shown in FIG. 1. The container 701 comprises a channelstructure 704 for conveying the printing material, the channel structuredefining an opening of the container 701. The channel structure 704 maybe based on channel structure 150 as described above. The channelstructure 704 may be for conveying the printing material from thecontainer 701 into the printing system during, or prior to, a printingoperation. The channel structure 704 may also be for conveying theprinting material from the printing system into the container 701,during a filling or refilling operation.

The container 701 comprises a material-conveying member 705 at leastpartially disposed within the channel structure 704. Thematerial-conveying member 705 is arranged to convey printing materialthrough the channel structure 704, e.g. either into or out of thecontainer 701. In this example, the material-conveying member is a helixscrew, however other configurations are possible. The helix screw may,for example, be a multi-helix screw such as a double helix screw. Thematerial-conveying member 705 is mounted to prevent rotation relative tothe channel structure 704. As such, rotation of the container 701 andits chamber also leads to rotation of the material-conveying member 705.For example, a notch in one of the material-conveying member 705 andchannel structure 704 may interface with a protrusion of the other ofthe channel structure 704 and the material-conveying member 705, wherebyto prevent relative rotation. Alternatively or additionally, relativemotion may be prevented by way of connecting means, for example anadhesive and/or a connecting member such as a bracket or screw, by whichthe material-conveying member 705 and channel structure 704 are joined.In some examples, the entire container 701 is configured to rotatetogether, such that there is no relative motion between thematerial-conveying member 705, the channel structure 704 and theremainder of the container 701. For example, the container 701 maycomprise helical raised portions to direct printing material to thechannel structure 704, or away from the channel structure 704, dependingon rotation direction as described elsewhere herein.

The channel structure 704 and the material-conveying member 705 arearranged to rotate together about a shared axis 706 to convey theprinting material through the channel structure. This may comprise theaxis 155 shown in FIG. 1. For example, the material-conveying member 705and the channel structure 704 may be arranged to rotate in a firstdirection to convey printing material into the container 701, and torotate in a second direction, opposed to the first direction, to conveyprinting material out of the container 701.

In certain cases, the use of a multi-helix screw as thematerial-conveying member 705 allows printing material to be collectedby the screw at more than one point over the course of a singlerotation. For example, a double helix screw collects printing materialat twice as many points during a rotation compared with a single helixscrew. The efficiency and speed of material conveyance is therebyimproved.

In some examples, printing material is supplied to thematerial-conveying member 705 from above or from the side. For example,during a refilling operation, recycled printing material may be fed tothe material-conveying member 705 by gravity from a nozzle located abovethe material-conveying member 705. In certain examples, the use of amulti-helix screw allows printing material to be collected at any pointin the rotation cycle. A single helix screw would not collect printingmaterial when the end of the screw thread is pointed away from thenozzle. This may cause the printing material to fall through the screw,from where it could be collected and returned to the nozzle. The use ofa multi-helix screw thus improves the efficiency of printing materialsupply, in particular in a refilling operation, as this reduces oravoids such collection and returning.

FIG. 7B shows schematically a valve structure 710 for a printingmaterial container, for example to be located within a channel structureof the container as described above.

The valve structure 710 comprises a seal 712 arranged circumferentiallyabout an axis of the valve structure. For example, the seal may comprisea compressible member such as a rubber O-ring.

The valve structure 710 comprises a material-conveying member 713aligned with an axis of the valve structure, for example configured asdescribed above in relation to FIG. 7A. The material-conveying member713 may be a double helix screw.

The seal 712 is arranged at a distal end of the material-conveyingmember 713, i.e. an end that in use is furthest from the interior of thecontainer. The material-conveying member 713 comprises a structure toprevent rotation relative to the opening of the printing materialcontainer. For example, the structure may comprise a notch or aconnecting means as described above.

The valve structure 710 is configured to be translatable within anopening of the printing material container, for example a channelstructure as described above in relation to FIG. 7A.

An example of such a translation is shown schematically in FIG. 7C. Inthe left-hand image 715, the valve structure 710 is positioned withinthe opening 718 of the printing material container such that the seal712 seals the opening 718. In the right-hand image 720, the valvestructure 710 is translated leftwards, such that the seal 712 does notseal the opening 718.

FIG. 7D shows schematically a container 701 comprising a valve 710 asdescribed above, mounted within a printing system 725. For example, theprinting system 725 may comprise printing system 200 and the container701 may be mounted within a material supply station such as materialsupply station 220 or 520 in FIGS. 3 to 5. The container 701 is held inplace by retaining members 726 a, 726 b of the printing system 725. Forexample, the retaining member may comprise sprung brackets or latches tohold the container 701. The container 701 is rotated about its axis in adirection 727 to convey printing material from the container 701 to areceiving element 728 of the printing system 725. This receiving element728 may be located within an intake of a material supply station asdescribed above. The receiving element 728 may be a funnel or hopperconfigured to receive the conveyed material, from which the printingmaterial is transferred to components of the printing system 725.

FIG. 7E shows schematically an end view of the container 701, mountedwithin the printing system 725. The container 701 is rotated in adirection 727 as described above. The container 701 is rotated, eitherdirectly or indirectly, by a rotating member 730 of the printing system725. For example, the rotating member may be a wheel that is rotated inorder to rotate the container 710 by friction or a cage that rotateswith the container being held within the cage. As another example, theretaining members 726 a, 726 b may be configured to move about thecentral axis of the container 701 and thereby rotate the container 701.Yet another example could be that of a timing pulley and belt to drivethe rotation.

FIG. 8 shows a method 801 of conveying a printing material between astorage container and a printing system, for example as described above.

The method 801 comprises at block 804 translating, within a channelstructure of the storage container, a valve structure from a proximalposition that seals the storage container to a distal position thatallows access to the storage container, for example as described abovein relation to FIG. 7C. For example, the container may be supplied to auser with the valve structure in the proximal position, such that thecontainer is sealed with printing material unable to escape. Thecontainer may further be sealed by a cap to be removed by the user, asdescribed in more detail below. The translating may be performed by atranslation element of the printing system, as described in more detailbelow.

The method 801 comprises, at block 805, rotating the storage containerabout a shared axis of the channel structure and a material-conveyingmember of the valve structure. As described above, this rotation causesprinting material to be conveyed in a direction of the shared axisbetween the storage container and the printing system. For example, theprinting material may be conveyed from the printing system to thecontainer, in a filling or refilling operation, or from the container tothe printing system, in a supply operation.

In examples, the storage container may be rotated at a different rate ina filling operation compared to a supply operation. For example, duringa supply operation, the container may be rotated at a rate between 40and 60 revolutions per minute. During a filling operation, the storagecontainer may then be rotated at a faster rate, the faster rate beingsufficiently high to cause the printing material to occupy an externalregion of the channel structure, by way of centrifugal force. Thiseffectively causes the printing material to fill the channel structurefrom the outside inwards. Filling the channel structure in this mannerreduces the number of gaps in the material flow, and thereby causes amore even stream of printing material into the container. This improvesthe efficiency of the filling operation. In one such example, a fillingoperation comprises rotating the container at a rate of between 80 and120 revolutions per minute.

In some examples, following the rotation described above, the method 801comprises translating, within the channel structure of the storagecontainer, the valve structure from the distal position (that allowsaccess to the storage container) to the proximal position (that sealsthe container). The container can thus be sealed following the fillingor supply operation, in order to prevent spillage of printing materialwhen the container is removed from the printing system.

In some examples the method 801 comprises, after translating the valvestructure from the distal position to the proximal position, coupling acap to an opening of the channel structure such that the cap exerts acontact force on the valve structure, wherein the contact forcecompresses a member of the valve structure within the channel structureto seal the storage container. This improves the effectiveness of thesealing, as described in more detail below.

Aspects of a further example container will now be described withreference to FIGS. 9A to 9E. FIGS. 9A to 9E show further configurationsof a channel structure of an example container. The aspects describedbelow may be used independently, or in combination with one or more ofthe other aspects and variations described herein.

FIG. 9A shows schematically a container 901 for storing a printingmaterial for a printing system. The container may comprise animplementation of container 100 from FIG. 1 and/or container 701 fromFIGS. 7A to 7E. The container 901 comprises a channel structure 903 forconveying the printing material. For example, this may comprise animplementation of the channel structure 150 in FIG. 1 or 704 in FIG. 7A.The channel structure 903 provides an opening of the container 901 andan axis 904 of the channel structure 903 defines an axial direction.Axis 904 may comprise axis 155 as shown in FIG. 1.

The container 901 comprises a valve structure 906 disposed within thechannel structure 903. The valve structure 906 may be implemented by thevalve structure 710 shown in FIGS. 7B and 7C or an alternativestructure. The valve structure 906 is translatable within the channelstructure between a proximal position and a distal position in the axialdirection, as described above. The proximal position may comprise aposition wherein the valve structure 906 is closest to the center of thecontainer, e.g. as shown in FIG. 9B. The distal position may comprise aposition wherein the valve structure 906 is located away from the centerof the container, e.g. as shown in FIG. 9A wherein the valve structure906 projects from the channel structure 903.

The valve structure 906 is further non-rotatable relative to the channelstructure 903 about the axis of the channel structure. For example,relative rotation of the valve structure 906 and the channel structure903 may be prevented by way of an element such as a notch in the valvestructure 906 that interfaces with a protrusion of the channel structure903 or, similarly, a notch in the channel structure 903 that interfaceswith a protrusion of the valve structure 906.

The valve structure 906 is shown in the distal position in FIG. 9A. Theamount of projection from the channel structure 903 in the distalposition may vary according to different implementations and intakeconfigurations. In the present example, the distal position allowsaccess to the interior of the container 901, for example for conveyanceof printing material from the container 901 to a printing system, orfrom the printing system to the container 901. The printing system inthis case may be printing system 200 as shown in FIG. 2.

FIG. 9B shows the container 901, with the valve structure 906 in theproximal position. The valve structure 906 is configured to seal thechannel structure when the valve structure 906 is in the proximalposition, thereby preventing conveyance of printing material. The valvestructure 906 may thus be used to prevent or allow conveyance ofprinting material, depending on its position relative to the channelstructure 903. For example, the valve structure 906 may be placed intothe proximal position during storage, shipping and/or handling toprevent spillage of printing material.

In some examples, the valve structure 906 comprises a material-conveyingmember aligned with the axis 904 of the channel structure. Thematerial-conveying member may, for example, comprise a multi-helix screwas described in more detail above. Such a valve structure can thereforeprevent conveyance of printing material when in the proximal position,and facilitate conveyance of printing material via a screw action whenin the distal position.

In examples, the valve structure 906 comprises a compressible member.The compressible member is arranged to seal the channel structure whenthe valve structure is in the proximal position. The compressible membermay be positioned circumferentially around a part of the valve structure906, for example in such a position as to be between said part of thevalve structure 906 and the interior of the channel structure 903 whenthe valve structure 906 is in the proximal position. For example, thecompressible member may be a rubber O-ring.

In examples, a cap is couplable to the container 901. FIG. 9C showsschematically such an example with a cap 910 coupled to the container901. Coupling the cap to the container exerts a force on the valvestructure 906, to push the valve structure 906 into the proximalposition. The compressible member described above is thus compressibleby coupling the cap 903 to the container, whereby to close the openingof the container. In this manner, the coupling of the cap to thecontainer ensures a secure sealing of the channel structure 903,reducing the risk of spillage of printing material. The presence of thecap 910 also provides a visual indication to a user that the valvestructure 906 is properly positioned to seal the channel structure 903.The presence of the cap 910 further acts to maintain the valve structure906 in the proximal position, for example during shipping of thecontainer 901.

In examples, the user manually de couples the cap 910 from the container901 prior to inserting the container 901 into the printing system. Thecompressible member may be configured to remain compressed followingdecoupling of the cap from the container. The seal is thus maintainedfollowing decoupling of the cap. This reduces the risk of spillage ofprinting material, for example if the user drops the container 901 whileloading it into the printing system.

FIG. 9D shows schematically an example container 901 loaded into aprinting system 915. For example, this may correspond to the insertionof container 100 as shown in FIG. 3, in particular the coupling to theintake 320 as shown in the third stage 303. This may also (oralternatively) correspond to the arrangement shown in FIG. 7D. The valvestructure 906, shown in the proximal position, is configured to betranslated within the channel structure by a translation member 916 ofthe printing system. The translation member 916 may form part of amechanical coupling of a material supply system such as 220.

FIG. 9E shows schematically said example container 901 loaded into theprinting system 915, the valve structure 906 having been translated indirection 917 into the distal position by the translation member 916.The valve structure 906 can thus remain in the proximal position,sealing the channel structure, until the container 901 is loaded intothe printing system 915. Spillage of printing material during theloading operation is thereby averted. In some examples, the valve member906 is further configured to be translated by the translation member 916from the distal position to the proximal position prior to removing thecontainer 901 from the printing system 915, thereby averting or reducingthe spillage of printing material during and following removal of thecontainer 901 from the printing system 915.

In some such examples and as depicted in FIGS. 9D and 9E, the valvestructure 906 comprises an engagement member 918 configured to beengaged by the translation member 916 of the printing system. Theengagement member may, for example, comprise a fastener, such as ascrew, and a washer configured to distribute the load of the fastener.In some such examples, the translation member 916 comprises jawsconfigured to engage with the engagement member 918.

An example cap for a printing material container, for example toimplement cap 910 as shown in FIG. 9C, will now be described withreference to FIGS. 9F and 9G.

FIG. 9F shows schematically a cross-section of a cap 951 for a printingmaterial container. The cap 951 comprises a coupling mechanism 955 tocouple the cap 951 to a channel structure of the printing materialcontainer. For example, the coupling mechanism 955 may, as shown,comprise a threaded structure, i.e. a screw thread, configured tointerface with a corresponding threaded structure of the printingmaterial container. Alternatively or additionally, the couplingmechanism 955 may comprise a latch or other means to fasten the cap 951to the printing material container.

The cap 951 comprises a raised portion 957 extending from an innersurface of the cap 951 in an axial direction. The raised portion 957 isconfigured to exert a contact force on a valve structure disposed withinthe channel structure when the cap 951 is coupled to the channelstructure. This contact force compresses a member of the valve structureto seal the printing material container, for example as described abovein relation to FIG. 9C.

FIG. 9G shows schematically the cap 951 coupled to a channel structure960 of a printing material container. As described above, the couplingcauses the raised portion 957 to exert a contact force on a valvestructure 962 disposed within the channel structure. This pushes thevalve structure 962 into a proximal position in which the channelstructure 960 is sealed. If the coupling mechanism 955 comprises a screwthread, screwing the cap 951 onto the channel structure applies thecontact force to the valve structure 962.

The coupling of the cap 951 to the channel structure 960 thus ensuresthat the valve structure 962 is positioned to securely seal the channelstructure 960, preventing or reducing the leakage of printing materialfrom the container through the channel structure 960. The presence ofthe cap 951 also provides a visual indication that the container issealed.

In some examples, the raised portion 957 is configured to couple with areceiving structure of the valve structure 962. For example, the raisedportion 957 may couple with a corresponding seat portion of the valvestructure 962. This improves the accuracy of the coupling between theraised portion 957 and the valve structure 962, thereby increasing theaccuracy of positioning the valve portion in the proximal position. Thereceiving structure may form part of the engagement member 918 asdescribed above.

In examples, a kit may be provided, the kit comprising a container and acap as described above.

FIG. 10 shows schematically a method 1001 of sealing a printing materialcontainer, for example a container as described above.

The method 1001 comprises, at block 1004, translating a valve structureto a proximal position in a channel structure of the printing materialcontainer, whereby to seal the channel structure as described above.

The method 1001 then comprises, at block 1005, exerting a contact forceon the valve structure via a raised portion of a cap coupled to theprinting material container. This block may comprise coupling a cap tothe printing material container. The raised portion of the cap exerts acontact force on the valve structure. As described above, the contactforce compresses a compressible sealing member of the valve structure,for example a rubber O-ring.

Certain examples of a container as described herein may be formed fromat least two initially separate components. This is shown in FIG. 11.FIG. 11 shows a first view of an example container 1101 duringmanufacture. The container 1101 comprises a chamber 1110 and a base1120. The chamber 1110 comprises a body portion of the example container1101 and may provide a side wall and closed end such as the inner wall120 and the closed end 140 in FIG. 1. The chamber 1110 in FIG. 11 has anopen end 1115. The open end 1115 may comprise an aperture substantiallyequal to the diameter of the container 1110, or at least wider than thecomparative opening 135 in FIG. 1. The base 1120 provides an opening1135 and a channel structure 1150. The opening 1135 may be formed withinthe channel structure 1150 as shown.

In these examples, the base 1120 is configured to be inserted into theopen end 1115 of the chamber 1110. For example, the base 1120 may beconsidered as a cover or lid for the container. FIG. 11 shows an examplecontainer 1102 formed from the base 1120 and the chamber 1110. Incertain cases, the base 1120 may be affixed to the chamber 1110following insertion, e.g. by glue and/or welding. An example method ofwelding the base 1120 to the chamber 1110 is described in more detailbelow. Having a base 1120 separate from the chamber 1110 may enabledifferent methods of manufacture to be used for each section of thecontainer. It may also allow different features to be present in eachsection. The examples below discuss some of these features. It should benoted that the functional aspects of the features below may alternativebe implemented in an integral single-unit container and/or a containerwith more than two components.

The term “base” is used herein to denote a separate component from amain chamber of the container; it need not relate to the bottom of thecontainer. In certain cases, the container may be stored or restedvertically upon the base, e.g. if a handle is provided at an oppositeclosed end of the chamber.

An example of a base for a printing material container will now bedescribed with reference to FIGS. 12A-C. FIG. 12A shows a schematictop-down view of the base 1201. FIG. 12B shows a cross-section of thebase 1201, viewed from the direction of the arrow labelled V2 in FIG.12A. FIG. 12C shows an isometric view of the base 1201 viewed from adirection between the viewing direction of FIG. 12A and that of FIG.12B.

In the present examples, base 1201 comprises a channel structure 1203defining an opening of the base 1201. For example, the channel structure1203 may implement channel structures 150 or 1150 to provide openings135 or 1135 as shown respectively in FIGS. 1 and 11. In this example,the channel structure 1203 comprises an open-ended cylinder, e.g. as maybe seen in FIG. 12B. In other examples, the channel structure is notcylindrical, and is instead shaped as an open-ended prism having aregular or irregular polygonal cross-section. A channel structure may besymmetric about an axis or may not be symmetric about an axis. A channelstructure may have a cross-section that varies along an axis, forexample a channel structure may be conically-shaped.

An axis 1205 of the channel structure 1203 defines an axial direction.This may implement the axis 155 described with reference to FIG. 1. Forexamples in which a channel structure is not symmetric about an axis, anaxis of the channel structure may be defined as an axis of an opening ofthe base 1201.

In the present example, a material-guiding structure 1204 is formedaround the opening of the base 1201. The material-guiding structure 1204has a helical lower surface 1207 that extends from the channel structure1203 in the axial direction, as shown in FIG. 12C. For example, thematerial-guiding structure may be seen as a “screw scoop”. The helicallower surface 1207 is shaped as a portion of a helicoid, truncated inthe axial direction and in the radial direction. Accordingly, the axialposition of any point on the helical lower surface 1207 with respect toa fixed point on the axis 1205 varies linearly with the angular positionof the point about the axis 1205. In other examples, a helical lowersurface may not be shaped as a portion of a helicoid, and the axialposition of any point on a helical lower surface may vary according to adifferent functional relationship. For example, the axial position ofany point on a helical lower surface with respect to a fixed point on anaxis may vary such that the pitch of the helical lower surface varieswith the angle about an axis. The pitch of a helical surface is theaxial distance occupied by a curve segment on the helical surface thatsubtends an angle of one full rotation about the axis of the helicalsurface. The material-guiding structure 1204 may have a function whenperforming one or more of supplying printing material from the containerand filling the container with printing material. In the former case,the material-guiding structure 1204 may “scoop” printing material anddeposit it into a material-conveying member. In the latter case, a“scoop” or interior volume of the material-guiding structure 1204 mayreceive material from the material-conveying member during rotation andguide this material to the start of helical ribs or flighting within thecontainer.

In one example, a pitch of the helical lower surface 1207 is chosen suchthat during a process of conveying printing material from a storagecontainer comprising the base 1201 to a printing system, a desiredamount of printing material is transferred for a given revolution of thestorage container, as will be described hereafter.

An upper surface of the material-guiding structure 1204 is formed by alower surface 1209 of the base 1201. In this example, the lower surface1209 of the base 1201 is substantially conical such that each point onthe lower surface 1209 of the base 1201 has a normal that makes anon-zero angle with the axial direction. In other examples, an uppersurface of a material-guiding structure has a normal that is alignedwith the axial direction, e.g. is flat. In other examples, an uppersurface of a material-guiding structure is helical. For example, anupper surface of a material-guiding structure may have substantially thesame shape as a helical lower surface of the material-guiding structure.In yet other examples, the upper surface of a material-guiding structuremay be separate from a surface of the base, e.g. the “scoop” portion maybe provided as a separate component that is fastened or otherwisecoupled to the base or container.

In FIGS. 12A-C, the helical lower surface 1207 meets the lower surface1209 of the base 1201 at a curved side wall 1211 that extends radiallyfrom the channel structure 1203 to an annular portion 1213 of the base1201. In this example, the outer surface of the annular portion 1213 ofthe base is conical. In other examples, the outer surface of an annularportion of a base is cylindrical.

In the example of FIGS. 12A-C, the curved side wall 1211 forms a curveof narrowing radius. In particular, the radial distance of the curvedside wall 1211 from the axis 1205 decreases from a maximum radius r₂ ata first angular position to a minimum radius r₁ at a second angularposition. In this example, the curved side wall 1211 subtends an angleof one full rotation about the axis 1205 so that the first angularposition is the same as the second angular position. In other examples,the curved side wall subtends an angle of less than one full rotationabout the axis 1205. For example, the radial distance of a curved sidewall may decrease from a maximum value to a minimum value in half of arotation. In other examples, the curved side wall subtends an angle ofmore than one full rotation about the axis 1205. For example, the curvedside wall may decrease from a maximum radius to a minimum over multiplefull rotations.

In the example of FIGS. 12A-C, the maximum radius r₂ of the curved sidewall 1211 is between two and four times the minimum radius r₁ of thecurved side wall 1211. More specifically, in this example the maximumradius r₂ of the curved side wall 1211 is approximately 9 cm and theminimum radius r₁ of the curved side wall 1211 is approximately 3 cm, soin this example the maximum radius r₂ of the curved side wall 1211 isapproximately three times the minimum radius r₁ of the curved side wall1211. The ratio of the maximum radius r₂ to the minimum radius r₁ ischosen such that during a process of conveying printing material from astorage container comprising the base 1201 to a printing system, adesired amount of printing material is transferred for a givenrevolution of the storage container, as will be described hereafter. Forexample, this may be achieved when a given quantity of printing materialis present in the container. The material-guiding structure may bedesigned to have a predefined volume to achieve this.

The narrowing radius of the curved side wall 1211 is a continuouslynarrowing radius. In this example, the radial distance of the curvedside wall 1211 from the axis 1205 decreases continuously with increasingangular separation from the part of the curved side wall 1211 having amaximum radius r₂. Furthermore, in this example the radial distance ofthe curved side wall 1211 from the axis 1205 decreases smoothly suchthat there are no corners in the curved side wall 1211. The continuouslynarrowing radius of the side wall 1211 allows for printing material tobe smoothly conveyed during a process of conveying printing materialfrom a storage container comprising the base 1201 to a printing system,resulting in the printing material being conveyed with an evenconsistency, and not having variations in consistency that may otherwisebe caused if the side wall 1211 did not have a continuously narrowingradius.

In the example of FIGS. 12A-C, the material-guiding structure 1204 is anintegral molded element of the base 1201. In this example, the base 1201is formed during an injection molding process. In other examples, a baseis formed by other molding processes, for example structural foammolding or compression molding. In other examples, a base is formedduring a first process, a material-guiding structure is formed during asecond process, and the base and the material-guiding structure are thenattached to each other, for example by screw-fit or snap fit techniques,or using a welding technique.

The material-guiding structure 1204 of base 1201 is configured to conveyprinting material to a material-conveying member when the base isrotated about the axis of the channel structure 1203. For example, thismaterial-conveying member may comprise the multi-helix screw 710 asshown in FIGS. 7A to 7E. The material-conveying structure may be locatedwithin the opening formed in the channel structure 1203. In thisexample, the base 1201 is configured such that when it is oriented withthe axis 1205 substantially horizontal, and with the region of thecurved side wall 1211 with the maximum radius r₂ vertically below theaxis 1205, then rotated in the direction indicated in FIGS. 12A and 12C,printing material may be guided along the material-guiding structure1204 towards a material-conveying member at least partially disposedwithin the channel structure 1203.

In examples in which a material-guiding structure is configured toconvey printing material to a material-conveying member when the base isrotated about the axis of a channel structure, the material-conveyingmember is configured to convey printer material through the channelstructure. In the example of FIGS. 12A-C, a material-conveying membermay be provided that is translatable in the axial direction within thechannel structure 1203 of the base 1201. In other examples, amaterial-conveying member may be provided that is fixed in an axialdirection with respect to a channel structure of a base for a printingmaterial container. In some examples, a material-conveying member isprovided as an integral molded element of a base for a printing materialcontainer.

In some examples in which a material-conveying member is configured toconvey printer material through the channel structure of the base 1201of FIGS. 12A-C, the material-conveying member is a multi-helix screw atleast partially disposed within the channel structure, as previouslydescribed. In a more specific example, the multi-helix screw is adouble-helix screw.

In some examples, the material-conveying member is configured to conveyprinting material through the channel structure 1203. In the exampledescribed above, the multi-helix screw has a fixed orientation withrespect to the base 1201, and is thereby configured to rotate with thebase 1201 about the axis 1205 of the channel structure 1203, causingprinting material to be conveyed through the channel structure.

In the example of FIGS. 12A-12C, the material-guiding structure 1204 isconfigured to guide a discrete dose of material, e.g. when certainmaterial fill conditions are met. In this example, the material-guidingstructure 1204 is configured such that when the base 1201 is orientedwith the axis 1205 substantially horizontal, and with the region of thecurved side wall 1211 with the maximum radius r₂ vertically below theaxis 1205, then rotated by one full rotation in the direction indicatedin FIGS. 12A and 12C, a discrete dose of printing material may be guidedalong the material-guiding structure 1204. Providing that the anglesubtended by the curved side wall 1211 about the axis 1205 is one fullrotation causes a discrete dose of printing material to be guided whenthe base 1201 is rotated by one full rotation, as all of the printingmaterial that enters the material-guiding structure may be guided to thechannel structure 1203. In other examples, the angle subtended by acurved side wall is less than a full rotation. In these examples, thematerial-guiding structure may be configured to guide a discrete dose ofprinting material when the base is rotated by less than a full rotation.

A method of conveying a printing material between a storage containerand a printing system will now be described with reference to FIGS. 12Dand 12E, which respectively show cross sections of a storage container1215 in two different orientations, and FIG. 13, which shows blocks ofthe method 1301. At block 1304, the method comprises providing a storagecontainer 1215 with an integral scoop 1217, the integral scoop 1217being arranged around a channel structure 1219 of the storage container1215. This may comprise supplying a filled storage container 1215 to alocation of use. In this example, the storage container 1215 issubstantially cylindrical and has an axis 1221. In other examples, astorage container is provided that is not cylindrical or generallycylindrical. In this example, the channel structure 1219 is anopen-ended cylinder. In other examples, a storage container is providedwith a channel structure that is not an open-ended cylinder, asdescribed above with reference to FIGS. 12A-C. The integral scoop 1217may comprise the material-guiding structure 1204 as shown in FIGS.12A-C.

The integral scoop 1217 has a helical floor 1223 that surrounds anopening of the channel structure 1219. In this example, the helicalfloor 1223 is shaped as a portion of a helicoid, truncated in the axialdirection and in the radial direction. Accordingly, the axial positionof any point on the helical floor 1223 with respect to a fixed pointvaries linearly with the angular position of the point about an axis1221 of the container 1215. In other examples, a helical lower surfacemay not be shaped as a portion of a helicoid, as described above withreference to FIGS. 12A-C.

A join 1225 between the helical floor 1223 and a surface 1227 of thestorage container 1215 forms a curve of narrowing radius. In thisexample, the radial distance of the join 1223 from the axis 1205decreases from a maximum radius at a first angular position to a minimumradius at a second angular position. In this example, the join 1225subtends an angle of one full rotation about the axis 1205 so that thefirst angular position is the same as the second angular position. Inother examples, the join subtends an angle other than one full rotation.

At block 1305, the method comprises rotating the storage container 1215about the axis 1221. In this example, the axis 1221 is substantiallyhorizontal. In other examples, a storage container may be rotated aboutan axis that makes a non-zero angle with the horizontal. In someexamples, a storage container may be oriented such that an end of thestorage container comprising the channel structure is lower than anopposite end of the storage container. Rotation may be performed in amanner similar to that illustrated in FIG. 4.

Rotation of the storage container 1215 rotates the integral scoop 1217within the storage container 1215 to convey the printing materialbetween the channel structure 1219 and an interior of the container1215. For example, the integral scoop 1217 may be fixably mounted withinthe storage container 1215 such that rotation of the storage container1215 rotates the integral scoop 1217 at the same speed, e.g. theintegral scoop 1217 is fixed with respect to the container housing. Inthe example of FIG. 12D, the storage container 1215 is initiallyoriented such that the portion of the join 1225 with the maximum radialdistance from the axis 1221 is vertically below the axis 1221. In thisorientation, an open portion of the integral scoop 1217 is underneath atop surface of printing material 1229.

The storage container 1215 is rotated in the direction indicated by thearrows in FIG. 12D. After the storage container 1215 has been rotated byhalf of a rotation, some of the printing material 1229 has been conveyedfrom the interior of the container 1215 to the channel structure 1219(where the black dots in FIGS. 12D and 12E represent printing materialparticles), and the storage container 1215 is oriented as shown in FIG.12E. After the storage container 1215 has been rotated by a further halfrotation, more of the printing material 1229 has been conveyed from theinterior of the container 1215 to the channel structure 1219, and thestorage container is again oriented as in FIG. 12D.

In another example, the storage container 1215 is rotated in a seconddirection that is opposite to the direction indicated by the arrows inFIG. 12D. When the storage container 1215 is rotated in the seconddirection, printing material is conveyed from the channel structure 1219to the interior of the storage container 1215.

The rotation of the storage container 1215 causes the integral scoop1217 to operate as an Archimedes screw, whereby to convey the printingmaterial 1229. In the example of FIG. 12D, when the storage container1215 rotates in the direction indicated by the arrows, the helical floor1223 conveys printing material towards the channel structure 1219 in adirection of the axis 1221.

In some examples, rotating the storage container 1215 comprisesconveying at least one discrete dose of printing material. Duringoperation of a printing system, several discrete doses of printingmaterial may be conveyed.

In the example of FIGS. 12D and 12E, conveying at least one discretedose of printing material may comprise conveying a single dose ofprinting material for a given 360-degree rotation of the storagecontainer. In this example, the storage container 1215 starts in theorientation shown in FIG. 12D, and a discrete dose of printing materialis conveyed when the storage container 1215 undergoes one full360-degree rotation in the direction indicated by the arrows in FIG.12D. In other examples, a discrete dose is conveyed when a storagecontainer is rotated by multiple 360-degree rotations. In otherexamples, a discrete dose is conveyed when a storage container isrotated by less than a 360-degree rotation.

In some examples, the method of conveying a printing material between astorage container and a printing system comprises conveying printingmaterial to a material-conveying member at least partially disposedwithin the channel structure. In the example of FIGS. 12D and 12E, amulti-helix screw 1231 is partially disposed within the channelstructure 1219, and rotating the storage container 1215 in the directionindicated by the arrows causes the printing material 1229 to be conveyedto the multi-helix screw 1231. The multi-helix screw 1231 rotates withthe storage container 1215, causing printing material 1229 to beconveyed through the channel structure, as shown in FIG. 12E.

In some examples, the rotation of the storage container is performed bya rotating element of a printing apparatus. In some examples, a rotatingelement is an element that releasably couples to a storage container androtates in unison with the storage container. In other examples, arotating element is an element that does not rotate in unison with thestorage container. For example, a rotating element may comprise rollersthat are configured to abut an outer surface of a storage container.

Another example of a container for a printing system will now bedescribed with reference to FIG. 12F, which shows a cross section of acontainer 1233 for a printing system. In this example, the container1233 is substantially cylindrical. In other examples, a container is notsubstantially cylindrical, and is instead substantially shaped as aprism having a regular or irregular polygonal cross-section. A containermay be symmetric about an axis or may not be symmetric about an axis. Acontainer may have a cross-section that varies along an axis, forexample a storage container may be conically-shaped.

The container 1233 comprises a chamber 1235 for storing a printingmaterial. In this example, the chamber 1235 is substantiallycylindrical, i.e. is generally cylindrical and/or has at least one ormore substantially cylindrical portions. In other examples, a chamberfor storing a printing material is not substantially cylindrical. Achamber for storing a printing material may have a shape correspondingto the shape of an outer surface of the container.

The container 1233 comprises a material-conveying member. In thisexample, the material-conveying member is a multi-helix screw 1237.Specifically, in this example the multi-helix screw 1237 is adouble-helix screw.

The container 1233 comprises a base 1239. In this example, the base 1239is welded to a body portion 1241 of the container 1233. In otherexamples, a base may joined to a body of a container by a snap-fitmeans. In other examples, a base may be joined to a body of a containerby a screw-fit means.

The base 1239 comprises opening 1243 for receiving thematerial-conveying member (multi-helix screw 1237). A shared axis 1245of the opening 1243 and the material-conveying member (multi-helix screw1237) defines an axial direction of the container. The base comprises amaterial-guiding structure formed around the opening 1243, having ahelical lower surface 1247 that extends from the base 1239 into thechamber 1235 in the axial direction. The helical lower surface 1247 isshaped as a portion of a helicoid, truncated in the axial direction andin the radial direction. Accordingly, the axial position of any point onthe helical lower surface 1247 with respect to a fixed point on the axis1245 varies linearly with the angular position of the point about theaxis 1245. In other examples, a helical lower surface may not be shapedas a portion of a helicoid, and the axial position of any point on ahelical lower surface may vary according to a different functionalrelationship. For example, the axial position of any point on a helicallower surface with respect to a fixed point on the axis 1245 may varysuch that the pitch of the helical lower surface varies with the angleabout an axis.

A portion of an outer side wall 1249 of the material-guiding structureabuts an inner side wall 1251 of the chamber 1235. In this example, theportion of the outer side wall 1249 that abuts the inner side wall 1251abuts a curved inner side wall 1251 of the chamber 1235. In otherexamples, a portion of an outer side wall of a material-guidingstructure abuts a raised portion of an inner side wall of a chamber. Insome such examples, the raised portion is flat.

An upper surface of the material-guiding structure is formed by a lowersurface 1253 of the base 1239. In this example, the lower surface 1253of the base 1239 is substantially conical such that each point on thelower surface 1253 of the base 1239 has a normal that makes a non-zeroangle with the axial direction. In other examples, an upper surface of amaterial-guiding structure has a normal that is aligned with the axialdirection. In other examples, an upper surface of a material-guidingstructure is helical. For example, an upper surface of amaterial-guiding structure may have substantially the same shape as ahelical lower surface of the material-guiding structure.

The helical lower surface 1247 meets the lower surface 1253 of the base1239 at a curved side wall 1255 that extends radially from the channelstructure to the outer side wall. In this example, the curved side wall1255 forms a curve of narrowing radius. In particular, the radialdistance of the curved side wall 1255 from the axis 1245 decreases froma maximum radius at a first angular position to a minimum radius at asecond angular position. In this example, the curved side wall 1255subtends an angle of one full rotation about the axis 1245 so that thefirst angular position is the same as the second angular position. Inother examples, the curved side wall subtends an angle of less than onefull rotation about the axis 1245. For example, the radial distance of acurved side wall may decrease from a maximum value to a minimum value inhalf of a rotation. In other examples, the curved side wall subtends anangle of more than one full rotation about the axis 1245. For example,the curved side wall may decrease from a maximum radius to a minimumover multiple full rotations.

FIG. 14 shows an example container 1401 that comprises a rotatablechamber 1402 for storing printing material. The rotatable chamber 1402has an opening 1404 that in use receives a base such as shown in FIG.11. The rotatable chamber has an inner structure 1405. The innerstructure 1405 conveys the printing material between an interior of thecylindrical chamber 1402 and the opening 1404 during rotation of thecontainer 1401. In the example shown in FIG. 14, the inner structure1405 is a structural feature of the inner surface of the container wallof the cylindrical chamber 1402. As the container 1401 rotates the innerstructure 1405 rotates with the chamber 1402 to convey printing materialto and from the opening 1404. The inner structure 1605 may comprise aseries of helical ribs or protrusions to move printing material alongthe container 1601, either during supply or filling.

In certain cases, the inner structure 1405 forms a helix structure inthe inner surface of the container wall. In one case, the innerstructure 1405 forms a continuous helix structure within the innersurface. In another case, the inner structure 1405 is disjointed whereeach raised portion in a set of raised portions forms a partial helixstructure.

In one case, the inner structure 1405 conveys printing material betweenthe rotatable chamber and at least one material-conveying structureforming part of the base during rotation. The at least onematerial-conveying structure may comprise at least one of thematerial-conveying member and the material-guiding structure asdescribed herein. Further possible features of the inner structure aredescribed in more detail in the example of FIGS. 16A to C.

FIG. 15 shows a mold 1500 for a printing material chamber such as thecontainer 1401 shown in FIG. 14, according to an example. The moldcomprises a surface to define an outer wall 1501 of the printingmaterial chamber. In the example shown in FIG. 15 the outer wall 1501 ofthe printing material chamber defined by the mold 1500 is generallycylindrical. The outer wall 1501 comprises a closed portion 1502 at oneend and an open portion 1503 at the other end. According to examplesdescribed herein, the mold 1500 comprises one or more raised surfacefeatures 1504. The one or more raised surface features 1504 formcorresponding indentations in the outer wall of the printing materialchamber. The indentations form raised portions on an inner wall of theprinting material chamber. FIG. 15 shows the raised surface features1504 of the mold 1500 which define the corresponding indentations. Inthe example of FIG. 15 the raised surface features 1504 result in theformation of helical ribs or ‘flighting’ in the printing materialchamber. The indentations may comprise two sets of indentations, one setfor each side of the printing material chamber.

A further example container, comprising certain features, will now bedescribed with reference to FIGS. 16A to 16C and 17.

FIGS. 16A-C show schematically a container 1601 for storing a printingmaterial for printing. According to examples, the container 1601 is usedto contain printing material suitable for two-dimensional andthree-dimensional printing as described herein. The container 1601comprises a generally cylindrical chamber 1602 formed by a containerwall 1603. The chamber 1602 has an opening 1604 at one end. In theexample shown in FIGS. 16A-C, the container 1601 is closed at the otherend.

According to examples described herein the container 1601 comprises aninner structure 1605. The inner structure 1605 conveys the printingmaterial between an interior of the chamber 1602 and the opening 1604during rotation of the container 1601. In the example shown in FIGS.16A-C, the inner structure 1605 is a structural feature of the innersurface of the container wall 1603 of the chamber 1602. In otherexamples, the inner structure 1605 is a portion separate from thechamber and is removable from the container 1601. The inner structure1605 is non-rotatable relative to the chamber 1602 of the container1601. As the container 1601 rotates the inner structure 1605 rotateswith the chamber 1602 to convey printing material to and from theopening 1604. The inner structure 1605 may comprise a series of helicalribs or protrusions to move printing material along the container 1601,either during supply or filling.

In FIG. 16A, the container wall 1603 comprises an outer surface. Theouter surface of the container wall 1603 comprises a planar portion1606. According to an example, the planar portion 1606 extends across asubstantial proportion of the width and the length of container 1601 toform a base of the container 1601. In comparison to a generallycylindrical container, the container 1601 can be placed to rest stablyon a surface on the planar portion.

The planar portion 1606 further provides an orientation of the container1601. For example, the planar portion 1606 is used to align thecontainer 1601 in a material supply station, such as during an insertionoperation as shown in FIG. 3. The planar portion 1606 may be used toalign the container 1601 within a cage used for rotation. A generallycylindrical container provides no indication of an orientation of thecontainer 1601. In contrast, the described container 1601 is insertedinto a material supply station using the planar portion 1606 as aguiding structure to orientate the container 1601 during insertion. Forexample, a passageway forming part of the mounting 310 in FIG. 3 may bearranged with a flat surface to receive and guide planar portion 1606.Also, generally cylindrical containers are prone to rolling duringtransportation or storage. The planar portion 1606 provides a surface onwhich to rest the container 1601 during transportation or storage.

In the example of the container 1601 shown in FIGS. 16A-C, the innerstructure 1605 comprises a plurality of portions 1607 in the innersurface of the container wall 1603. The raised portions 1607 are raisedon the inside of the container 1601. In the example shown in FIGS.16A-C, the raised portions 1607 are positioned at intervals along thelength of the chamber 1602 and surround the chamber 1602. The raisedportions help to convey printing material between the interior of thechamber and the opening of the container during rotation of thecontainer.

In certain cases, the raised portions 1607 form a helix structure in theinner surface of the container wall 1603. In one case, the raisedportions 1609 are connected to form a continuous helix structure withinthe inner surface. In another case, the raised portions 1607 aredisjointed where each raised portion forms a partial helix structure.The raised portions 1607 pass through the planar portion 1606 on thebase of the container.

The raised portions 1607 forming the helix structure on the innersurface of the container 1601 help transfer printing material from theinterior of the chamber 1602 towards the opening 1604 of the container1601 when the container 1601 is rotated. Printing material that comesinto contact with the helix structure is moved by the helical portionsin a direction parallel to the axis of rotation of the container 1601.This reduces the amount of printing material that becomes stationarywith respect to the axial direction and encourages printing material tomove towards or away from the opening 1604 of the container 1601.

The helix structure on the container 1601 shown in FIGS. 16A-C extendsaround the chamber 1602 approximately four times. This number may varyin other examples. The helix is angled sufficiently to ensure aconsistent transfer of printing material in the container 1601 when thecontainer 1601 is rotated. In examples described herein, the rate oftransmission of printing material in the container 1601 is notsubstantially affected when the raised portions 1607 do not pass throughthe planar portion.

In certain cases, the raised portions 1607 are rounded. Rounding off theraised portion 1607 helps to ensure that printing material cannot becomestuck in or around the raised portions 1607. This reduces the risk ofprinting material becoming compacted or gather in a particular region ofthe container.

In the example of the container 1601 shown in FIGS. 16A-C, the container1601 comprises a handle portion 1608. The handle portion 1608 is formedat the closed end of the container 1601. The handle portion 1608 allowsa user to hold the container 1601 and position the container 1601 torest on the planar portion 1606 according to examples described herein.In the example of a container 1601 shown in FIGS. 16A-C, the handleportion 1608 comprises an elongate hand grip that extends in a directionsubstantially perpendicular to the planar portion 1606. This allows thecontainer 1601 to easily be gripped by a user and, in particular, helpsa user to align the container 1601 on the planar portion 1606 on aresting surface. Moreover, the grip is formed within the container 1601.This can be manufactured in the same process as the chamber of thecontainer 1601.

In some examples, the handle portion 1608 may comprise a wall thickness,hardness, toughness, and strength sufficient to withstand the loadedweight of build material within the handle portion 1608 and chamber1602, as well as resisting fracture and/or denting upon the container1601 being inadvertently mishandled (e.g. dropped, etc.). In someexamples, at least the handle portion 1608 may be formed of a polymermaterial, such as high density polyethylene (HDPE), any number ofdifferent polymers, or combinations thereof. In some examples, at leastsome these same materials may be used to form the chamber 1602.

In some examples, an inner wall surface of the handle portion 1608and/or of the chamber 1602 may comprise a low coefficient of friction.This arrangement may facilitate flowability of printing material withincontainer 1601, including handle portion 1608. In some examples, theinner wall surface of the handle portion 1608 and/or chamber 1602 maycomprise a lubricous coating to enhance such flowability.

In certain examples of the container 1601 described herein, such asshown in FIGS. 16A-C, the elongate hand grip is aligned at a non-zeroangle to a plane of a base of the cylindrical chamber 1602. In theexample shown in FIGS. 16A-C the handle portion 1608 is at an angle ofapproximately 60 degrees to the base of the container 1601 containingthe planar portion 1606. However, in other cases the elongate handleportion 1608 is angled at a different degree to the horizontal.

Angling the elongate handle portion 1608 with respect to a base portionallows a user to control the motion of the container 1601. Inparticular, the angled elongate handle portion 1608 gives an improvedweight distribution across the container 1601 when held by the handleportion.

According to examples described herein the planar portion 1606 of thecontainer 1601 further comprises a notch portion. The notch portion isan inwardly pointing indentation within the outer wall of the container1601. The notch portion is used to latch the container into a materialsupply station.

FIGS. 16B and 16C show two alternative views of the container 1601. FIG.16B shows a view of the container 1601 looking in from the opening 1604.In FIG. 16B the interior of the container 1601 is shown including theinterior portion of the elongated handle portion 1608. According toexamples, the interior of the elongated handle portion 1610 is hollow.Printing material may thus be stored in the handle portion 1610. FIG.16B also shows the planar portion 1608. The view of the container 1601shown in FIG. 16C shows a view of the exterior handle portion 1608 ofthe container. It can be seen from the view of the container 1601 shownin FIG. 16C that the handle portion 1608 extends in a directionsubstantially perpendicular to the planar portion 1606.

FIG. 17 shows a mold 1700 for a printing material chamber such as thecontainer 1601 shown in FIG. 16, according to an example. The moldcomprises a surface to define an outer wall 1701 of the printingmaterial chamber. In the example shown in FIG. 17 the outer wall 1701 ofthe printing material chamber defined by the mold 1700 is cylindrical.The outer wall 1701 comprises a closed portion 1702 at one end and anopen portion 1703 at the other end. The surface of the mold comprises aplanar portion 1704 projecting into the surface of the mold. When themold 1700 is used the planar portion 1704 defines a corresponding planarportion in the outer wall of the printing material chamber. The planarportion of the printing material chamber aligns the chamber on a restingsurface.

According to examples described herein, the mold 1700 comprises one ormore raised surface features 1705. The one or more raised surfacefeatures 1705 form corresponding indentation in the outer wall of theprinting material chamber. The indentations form raised portions on aninner wall of the printing material chamber. FIG. 17 shows the raisedsurface features 1705 of the mold 1700 which define the correspondingindentations. In the example of FIG. 17 the raised surface features 1705result in the formation of helical ribs or ‘flighting’ in the printingmaterial chamber.

In examples, the one or more raised surface features of the mold 1700are rounded. The rounded raised surface features form correspondingrounded raised portions in the inner wall of the printing materialchamber.

In the example of the mold shown in FIG. 17, the mold 1700 furthercomprises a channel to define a handle portion 1706. The handle portion1706 forms part of the closed end 1702 of the printing material chamber.The handle 1706 formed by the mold shown in FIG. 17 is an elongatehandle portion that is angled with respect to the planar portion,similar to the handle portion of the container shown in FIG. 16.

According to an example, the mold 1700 further comprises a notch portionthat projects in to the planar portion of the surface of the mold. Thenotch defines a corresponding notch portion in the outer wall of theprinting material chamber. The notch portion in the outer wall is usedto latch the printing material chamber in a material supply station.

A further example container, implementing examples of the presentdisclosure, will now be described with reference to FIGS. 18A and 18Band 19.

FIGS. 18A and 18B show schematically two views of a portion of acontainer 1801, e.g. for use with a material supply station of aprinting system, according to an example. The container may be any oneof the example containers described herein. FIG. 18A shows a viewlooking into an opening of the container 1801. The container 1801comprises a chamber 1802 for storing printing material and amaterial-guiding structure 1803. The material-guiding structure 1803 isformed around a channel structure 1804 of the container. Thematerial-guiding structure 1803 is arranged to guide printing materialbetween an interior of the printing material container 1801 and thechannel structure 1804 of the printing material container 1801 when thecontainer 1801 is rotated about a central axis, for example axis 155 inFIG. 1.

The printing material container 1801 shown in FIGS. 18A and 18Bcomprises a raised portion 1805 within an inner surface 1806 of thechamber 1802. FIG. 18B shows a close up view of the raised portion 1805and the material-guiding structure 1803. The raised portion 1805 isarranged to guide the printing material into an opening 1807 of thematerial-guiding structure 1803. In certain examples described herein,the material-guiding structure 1803 has a helical shape in the form ofan Archimedes screw that guides printing material towards the channelstructure 1804. The opening of the material-guiding structure 1803 formsa scoop shape which helps to transfer printing material towards thechannel structure 1804. The material-guiding structure 1803 may comprisethe material-guiding structure 1204 shown in FIGS. 12A-12F.

The raised portion 1805 helps to maximize the amount of printingmaterial that is deposited in the opening 1807 of the material-guidingstructure 1803 and minimize the amount of printing material that becomesstranded in the chamber 1802 as the container 1801 rotates in thematerial supply station. According to examples, the raised portion 1805is formed as an indentation in the inner wall of the container. In othercases, the raised portion is a separate portion that is attached to thecontainer 1801.

In examples described herein, the raised portion 1805 is adjacent in thecontainer 1801 to the material-guiding structure 1803. This is shown inFIG. 18B. The adjacency is with respect to an annular surface of thecontainer 1801 and the material-guiding structure 1803. The raisedportion 1805 may be as close as possible to the material-guidingstructure 1803 within the constraints imposed by a manufacturingprocesses of the container 1801. In particular, the opening of thematerial-guiding structure 1803 is almost flush to (i.e. abuts) theraised portion 1803. This further minimizes the amount of printingmaterial that becomes stranded in the container 1801 as it rotates.

In the example shown in FIG. 18B, the width of the raised portion 1805is equal to a width of the opening 1807 of the material-guidingstructure 1803, as indicated by the dotted arrow in FIG. 18B. Thismaximizes the amount of printing material which is transferred from theraised portion 1805 to the opening of the material-guiding structure1803. In other cases, the raised portion 1805 may have a width that isgreater than, or less than, the width of the opening 1807.

According to certain examples, the raised portion 1805 is a planarportion. In other words, the raised portion 1805 forms a raisedflattened platform on which printing material accumulates duringrotation of the container 1801. In this case, printing material istransferred to the opening of the container from the planar portion tothe material-guiding structure 1803 as the container rotates.

In further examples of the container 1800, the inner surface 1806 of thechamber 1802 comprises one or more “ribs” or “flighting” to guideprinting material to the opening of the material-guiding structure 1803.For example, these are shown in FIGS. 14 and 16A. The one or more ribsare comprised around the edge of the inner surface 1806 and, in certaincases, are formed as indentations in the inner surface during amanufacturing process of the container 1801, As described in relation toother examples of containers described herein, the ribs are in certaincases helical ribs that spiral around the inner surface of thecontainer. During rotation, the ribs encourage the motion of printingmaterial between an interior of the container 1801 and the opening ofthe container 1801.

In one example, one of the ribs is positioned such that it meets withthe raised portion 1805 in the inner surface 1806 of the container 1801.For example, in one case, a rib is manufactured into the inner surfacesuch that the rib blends into the raised portion 1805. In thisarrangement, printing material that is moved by the rib during rotationof the container is guided on to the surface of the raised portion 1805.

In a further example, the raised portion 1805 of the container 1801 hasa height above the inner surface of the chamber 1802, such that a planeof the raised portion 1805 and a plane of the opening of thematerial-guiding structure 1803 are substantially aligned. This is shownin FIG. 18B. This helps to ensure printing material does not becomestuck at the lip of the opening of the material-guiding structure 1803as the container 1801 rotates.

In certain examples described herein, the container 1801 comprises afurther planar portion which forms a base of the container, as describedin relation to FIGS. 16A-16C. The further planar portion extends alongthe length and the width of the container 1801. According to examples,the raised portion 1803 is formed in the further planar portion of thecontainer 1801. This simplifies a manufacturing procedure where thecontainer is constructed from a mold, since the raised portion 1803 canbe pressed into a flattened portion, as opposed to a cylindrical portionof the outer wall of the container 1801. In particular, in certainexamples the resulting manufacturing process produces a container 1801where the raised portion 1805 is planar. As described elsewhere, thewall of the container 1801 may be manufactured by blow-molding.

FIG. 19 is schematic diagram of a mold 1900 for a printing materialchamber according to an example. The mold 1900 is used in amanufacturing process such as those described herein. The mold 1900comprises a surface 1901 to define an outer wall 1902 of the printingmaterial chamber. The outer wall 1902 has a closed lower portion 1903and an open top portion 1904. The open top portion 1904 is dimensioned,i.e. sized appropriately, to receive a corresponding material-guidingstructure. The material-guiding structure may form part of a base 1120as shown in FIG. 11. According to examples described herein, the surface1901 of the mold 1900 comprises a raised portion 1905. The raisedportion 1905 forms a corresponding raised portion in an inner wall ofthe chamber to guide printing material into the material-guidingstructure, such as that shown in FIGS. 18A and 18B.

In an example, the surface 1901 of the mold 1900 comprising the raisedportion is positioned such that, when inserted into the opening 1904,the material-guiding structure is adjacent to the indentation formingthe raised portion in the inner wall of the printing material chamber.

In a further example, the surface 1901 comprises one or more ridges thatform indentations in the outer wall of the printing material chamber.The indentations form corresponding ribs within the inner wall of theprinting material chamber. The ribs guide printing material towards thematerial-guiding structure. In one case, the ridges form helicalportions on the surface 1901 of the mold 1900. The helical ridges form acorresponding helical ribs in the printing material chamber, e.g. asdescribed with reference to other examples.

In certain cases, one of the ridges is arranged to merge into the raisedportion 1905 of the mold 1900 such that the corresponding rib in theprinting material chamber contacts the raise portion. According toanother example of the mold 1900, the mold comprises a planar portion toform a corresponding planar portion within the inner wall of theprinting material chamber. In such a case, according to an example, themold 1900 is such that the raised portion is formed as a raised sectionof this planar portion. The resulting corresponding raised portion inthe printing material chamber is, in certain cases, also planar.

FIGS. 20A and 20B show methods of conveying printing material based onthe example containers of FIGS. 16A to 19.

FIG. 20A shows a method 2001 of conveying printing material such aspowder from a container according to an example. The method 2001 is usedwith the examples of containers described herein. At block 2001,printing material is conveyed along an axis from a closed end of thecontainer to an open end of the container via a set of helical ribs. Thehelical ribs are formed in the inner surface of the container. At block2002, printing material is transferred from the container into amaterial-guiding structure, the material-guiding structure having anopening in a plane containing the axis, wherein a distance between theinner surface and a side wall of the opening is spanned by a raisedportion within the inner surface.

The method 2001 and examples of the container 1800 described herein canbe used to minimize the amount of stranded printing material in thecontainer 1800 when the container is rotated in a material supplystation. The raised portion may be manufactured into the container 1800using the same processes that are used to manufacture the container 1800itself.

FIG. 20B shows a method 2010 of conveying printing material between aprinting material container comprising an elongate generally cylindricalchamber and a printing system, according to an example. At block 2011,the printing material container is aligned with a planar surface of aninsertion channel of a material supply station of the printing system.At block 2012, the printing material container is inserted into theinsertion channel of the material supply station. At block 2013, anopening of the printing material container is coupled to the materialsupply station. For example, this may follow the routine showed in FIG.3. At block 2014, the printing material container is rotated within thematerial supply station to convey, via an inner structure of theelongate cylindrical chamber, printing material between the printingmaterial container and the printing system. For example, this is shownin FIG. 4. The method 2010 is used in the context of examples describedherein. In particular the method is used with the container shown inFIGS. 16A-C.

In certain examples of the method 2010 described herein, aligning theplanar portion of the printing material container comprises gripping anangled handle at a closed end of the elongate generally cylindricalchamber and inserting the printing material container comprises applyinga force along an axis of the chamber via the angled handle.

An example of a method of manufacturing a container for a printingmaterial will now be described. The method may be used to manufacture acontainer as described in any of the examples set out herein.

FIG. 21A shows components of a container that may be used in the methodof manufacture. A first portion 2103 and a second portion 2105 areprovided. The first portion 2103 and the second portion 2105 maycomprise the base 1120 and chamber 1110 as described with reference toFIG. 12. In the present example, the first portion 2103 is substantiallyformed of a first material and the second portion 2105 is substantiallyformed of a second material, the first material and the second materialboth being thermoplastic materials. A thermoplastic material is amaterial that exhibits plastic behavior when its temperature is greaterthan a certain temperature, and is solid when its temperature dropsbelow the certain temperature. Certain synthetic polymers are examplesof thermoplastic materials. In this example, the first portion 2103 andthe second portion 2105 are substantially formed of different grades ofa single thermoplastic polymer. In other examples, a first portion and asecond portion may be substantially formed of the same grade of a singlethermoplastic polymer. Different grades of a polymer may have differentproperties, including different melting temperatures and differentviscosities. In further examples, a first portion and a second portionmay be substantially formed of different thermoplastic polymers.

In the example of FIG. 21A, the first portion 2103 and the secondportion 2105 are both substantially cylindrical in shape, such that thefirst portion 2103 and second portion 2105 have outer surfaces withcircular symmetry. In other examples, portions of differing shapes areprovided. For example, either one or both of the portions may have outersurfaces with regular or irregular polygonal cross-sections. Portionsmay have outer surfaces with cross sections that are symmetric about anaxis, or may have outer surfaces with cross sections that are notsymmetric about an axis. Portions may have cross-sections that varyalong an axis.

The first portion 2103 comprises a circular opening 2107 having an axis2109. The opening 2107 is circumscribed by an annular wall 2111. Theannular wall 2111 has circular symmetry about the axis 2109. In thisexample, the annular wall 2111 has a rim consisting of a flat uppersurface 2113 with a normal that is parallel to the axis 2109, referredto hereafter as an axial direction. In other examples, a first containerportion has an annular wall with a rim that does not have a flat uppersurface with a normal in an axial direction. For example, a firstcontainer portion may have an annular wall with an upper surface havinga normal that makes a non-zero angle with the axial direction, such thatthe upper surface is a conical surface. In some examples, a firstcontainer portion has a rim with a normal that varies with radialdistance from an axis of the portion. In some examples, a firstcontainer portion has a rim with more than one upper surface.

The second portion 2105 comprises an annular cavity 2115 for receivingthe annular wall 2111. In FIG. 21A, the first portion 2103 and thesecond portion 2105 are aligned coaxially, with axis 2109 arranged as anaxis of the annular cavity 2115. In this example, the annular cavity2115 is partially bounded by a radially outward-facing surface 2117 andby a lip 2119 that overhangs the radially outward-facing surface 2117.The annular cavity 2115 is thereby bounded in a radially inward-facingdirection, in a radially outward-facing direction, and in a first axialdirection. The annular cavity 2115 is operable to receive the annularwall 2111 from a second axial direction that is opposite to the firstaxial direction.

FIG. 21B shows a view from below of the second portion 2105. In thisexample, the container 2101 is operable to supply printing material to aprinting system, and the second portion 2105 has integral structuresoperable to perform the task of supplying printing material to theprinting system. In particular, the second portion comprises a channelstructure 2123 defining an opening to the second portion 2105, and amaterial-guiding structure 2125. Other examples of containers have otherintegral structures that depend on the purpose of the container.

FIG. 21C shows example cross sections of annular cavities for receivingan annular wall. Example (a) shows a cross section of the annular cavity2115 of the second portion 2105 of FIG. 21A, as viewed from a directionperpendicular to the axis 2109. In this example, the lip 2119 comprisesa member 2121 extending into the annular cavity 2115. The member 2121 isa bounding member of the annular cavity 2115, meaning that at least apart of the annular cavity 2115 is bounded in at least one direction bythe member 2121. In this example, the member 2121 is annular, having aradially inward-facing surface extending from a radially inward-facingsurface of the lip 2119, and a flat lower surface with a normal facingin the axial direction from which the annular cavity 2115 is operable toreceive the annular wall 2111. The member 2121 is configured for fusingwith an outer surface of the annular wall 2111, as will be describedhereafter. A member of a first portion that is configured for fusingwith a specific region of a second portion is referred to as an energydirector.

Example (b) of FIG. 21C shows a cross section of a different annularcavity 2127 comprised in a container portion for receiving an annularwall. In this example, an axially-facing surface 2129 extends between aradially outward-facing surface 2133 of the container portion and aradially inward-facing surface of a lip 2131 that overhangs the radiallyoutward-facing surface 2133. In this example, the axially-facing surface2129 is configured for fusing with a top surface of an annular wall. Theaxially-facing surface 2129 is an example of a bounding member of theannular cavity 2127.

Example (c) of FIG. 21C shows a cross section of a different annularcavity 2135 comprised in a container portion for receiving an annularwall. In this example, a bounding member 2139 of the annular cavity 2135extends from a radially outward-facing surface 2137 of the containerportion. In this example, the bounding member 2139 is configured forfusing with an inner surface of an annular wall.

Example (d) of FIG. 21C shows a cross section of a different annularcavity 2141 comprised in a container portion for receiving an annularwall. In this example, annular cavity 2141 is an indent in anaxially-facing surface 2143 of the container portion. In this example,the axially-facing surface 2143 is configured for fusing with a topsurface of an annular wall. The axially-facing surface 2143 is anexample of a bounding member of the annular cavity 2141.

Each of the examples of FIG. 21C includes an annular bounding member forfusing with an annular wall. Other examples include bounding membersthat do not have a circular symmetry. For example, a container portionmay have several bounding members for fusing with an annular wall, thebounding members being located at regular or irregular angular intervalswithin an annular cavity.

In the present example, the two portions are joined by advancing theannular wall into the annular cavity, e.g. by applying a compressiveforce in an axial direction of the opening. The first portion and thesecond portion are then temporarily rotated relative to each other tofuse the first and second portions. This is described in more detailbelow.

The flow diagram of FIG. 22 represents a routine by which the firstportion 2103 and the second portion 2105 are joined together to form thecontainer 2101. The routine begins by advancing, at 2201, the annularwall 2111 of the first portion 2103 into the annular cavity 2115 of thesecond portion 2105. In this example, a spin welding machine is used tohold to the first portion 2103 stationary and to advance the secondportion 2105 towards the first portion 2103 in an axial direction asshown by the straight arrows in FIG. 21A. As shown in stage (a) of FIG.21D, the annular wall 2111 is advanced into the annular cavity 2115 asthe second portion 2105 is advanced towards the first portion 2103. Inother examples, a spin welding machine is used to hold the secondportion 2105 stationary and to advance the first portion 2103 towardsthe second portion 2105 in an axial direction. In further examples, aspin welding machine is used to advance the first portion 2103 and thesecond portion 2105 towards each other.

The spin welding machine advances the annular wall 2111 into the annularcavity 2115 until the upper surface 2113 of the annular wall 2111 abutsa lower surface of the bounding member 2121, as shown in stage (b) ofFIG. 21D. The spin welding machine then continues to exert a compressiveforce between the first portion 2103 and the second portion 2105 in anaxial direction of the opening 2109 of the first portion 2103. In thisexample, the compressive force does not significantly deform either ofthe container portions.

The spin welding machine temporarily rotates, at 2203, the first portion2103 and the second portion 2105 relative to each other under thecompressive force. In this example, the spin welding machine holds thefirst portion 2103 stationary whilst temporarily rotating the secondportion 2105. In other examples, a spin welding machine holds the secondportion 2105 stationary whilst rotating the first portion 2103. Infurther examples, a spin welding machine temporarily rotates the firstportion 2103 and the second portion 2105 in opposite directions. Thespin welding machine temporarily rotates the container portions relativeto one another at a rate such that the relative tangential speed of thebounding member 2121 with respect to the annular wall 2111 issufficiently high to cause the abutting regions of the bounding member2121 and the annular wall 2111 to increase in temperature due tofriction such that they become plastic. The rate of rotation thereforedepends on the properties of the thermoplastic material from which thecontainer portions are formed. The rate of rotation also depends on theradius of the annular wall 2111 and accordingly the radius of theannular cavity 2115. In some examples, temporarily rotating a firstportion and a second portion relative to each comprises temporarilyrotating the first portion and the second portion at a relative angularvelocity of between 100 revolutions per minute and 1000 revolutions perminute. In the example of FIG. 21A, the radius of the annular wall isapproximately 10 cm and rotating the first portion 2103 and the secondportion 2105 relative to each other comprises rotating the secondportion 2105 at a rate of approximately 500 revolutions per minute.

The spin welding machine temporarily rotates the second portion 2105relative to the first portion 2103. In particular, the spin weldingmachine rotates the second portion 2105 relative to the first portion2103 until a sufficient fraction of the bounding member 2121 and theannular wall 2111 have become plastic that the annular wall 2111 isadvanced under the compressive force to a maximum axial displacementwithin the annular cavity 2115, as shown in stage (c) of FIG. 21D. Thefirst material of the first portion 2103 and the second material of thesecond portion 2105 have substantially equal melting rates, meaning thatduring the time that the second portion 2105 is rotated relative to thefirst portion 2103, the regions become plastic at substantially the samerate. The melting rate of a thermoplastic material depends on themelting temperature, as well as the viscosity of the material. The firstmaterial of the first portion 2103 and the second material of the secondportion 2105 are chosen to have substantially the same melting rate,although the first material and the second material are differentmaterials. This ensures that the bounding member 2121 and the annularwall 2111 become both become plastic along an interface between thebounding member 2121 and the annular wall 2111. As the bounding member2121 and the annular wall 2111 become plastic, the relative motion ofthe bounding member 2121 and the annular wall 2111 causes the plasticregions to mix, forming a mixed plastic region, referred to as a fusingregion, represented by the shaded region in stage (c) of FIG. 21D.

The configuration of the annular cavity 2115, in which the lip 2119overhangs the radially outward-facing surface 2117, and the boundingmember 2121 extends in a radially inward-facing direction from the lip,prevents plastic material, referred to as weld flash, from entering theinterior of the container 2101 as the second portion 2105 is temporarilyrotated relative to the first portion 2103. Preventing weld flash fromentering a container prevents the weld flash from contaminating theinterior volumes of the container. In some examples, the material thatthe container will be filled with may not be of the same type or form asthe weld flash, and in such examples it may not be acceptable for weldflash to enter the container.

The spin welding machine arrests, at 2205, the relative rotation betweenthe first portion 2103 and the second portion 2105 at a predeterminedrelative angle between the first portion 2103 and the second portion2105. In this example, the predetermined angle is accurate to withinless than one degree. Arresting the relative rotation between the firstportion 2103 and the second portion 2105 at a predetermined angle isreferred to as clocking. In this example, the first portion 2103 and thesecond portion 2105 both have integral features, such as thematerial-guiding structure 2125, and these integral features have analignment in order for the container to be operable to supply printingmaterial to a printing system. In other examples, such as those forwhich at least one of the first portion and the second portion havecylindrical symmetry, the relative motion may be arrested at anarbitrary angle.

The spin welding machine arrests the relative rotation between the firstportion 2103 and the second portion 2105 substantially instantaneously.This means that the relative rotation is arrested in a time intervalthat is much shorter than the time taken for the plastic material tocool and fuse. In this example, the relative rotation is decreased froma maximum relative rate of rotation to zero in less than one tenth of asecond. Arresting the relative rotation between the first portion 2103and the second portion 2105 substantially instantaneously causes theplastic material to cool evenly, preventing the formation of particlesduring the cooling process that may weaken a resulting weld formedbetween the first portion 2103 and the second portion 2105.

After arresting the relative rotation between the first portion 2103 andthe second portion 2105, the spin welding machine holds the firstportion 2103 and the second portion 2105 in place and allows, at 2207,the fusing region to cool, thereby fusing and creating a weld betweenthe first portion 2103 and the second portion 2105.

In the example of FIG. 21A, providing the first portion 2103 comprisesforming the first portion 2103 by blow molding. Forming the firstportion 2103 by blow molding results in the first portion havingprecisely-controllable outer dimensions and less precisely-controllableinner dimensions. In particular, the radially outward-facing surface ofthe annular wall 2111 is more precisely cylindrical than the radiallyinward-facing surface of the annular wall 2111. Therefore, the boundingmember 2121 fuses with the more precisely-controlled surface of theannular wall 2111, resulting in a more reliable weld. In other examples,other molding processes are used to form a first portion having anannular wall. Examples of other molding processes that may be used arecompression molding, injection molding, and structural foam molding.

In the example of FIG. 21A, providing the second portion 2105 comprisesforming the second portion 2105 by injection molding. Forming the secondportion 2105 by injection molding results in precisely-controllabledimensions of all of the surfaces of the second portion 2105. In otherexamples, other molding processes are used to form a second portionhaving an annular cavity for receiving an annular wall. Examples ofother molding processes that may be used are compression molding andstructural foam molding.

Due to the respective molding processes used to form the first portion2103 and the second portion 2105, the first material that substantiallyforms the first portion 2103 is more viscous than the second materialthat substantially forms the second portion 2105. For blow molding, arelatively viscous plastic material is used to form a parison into whicha gas is blown, causing the exterior surface of the parison to adhere tothe inner wall of a mold, before the plastic material cools andsolidifies. For injection molding, a less viscous plastic material isinjected into a mold such that the plastic material entirely fills themold, before the plastic cools and solidifies. As discussed above, inthe example of FIG. 21A, the melting rates of the first material and thesecond material, which depend on the viscosity, are chosen to besubstantially the same.

As such in certain examples a container for storing a printing materialsuch as a powdered build material is presented that comprises ablow-molded rotatable chamber for storing the powdered build materialand an injection-molded base comprising an opening for conveying theprinting material between an interior and exterior of the container. Inthis case, the injection-molded base is mounted within an open end ofthe blow-molded rotatable chamber and the injection-molded basecomprises an annular cavity that receives an annular wall of theblow-molded rotatable chamber, wherein the blow-molded rotatable chamberis fused to the injection-molded base via a spin weld.

FIG. 23 is an exploded isometric view of an example container 2300 thatcombines certain features described above. The container comprises agenerally cylindrical chamber 2310 of diameter D, and length L. Thecontainer has internal helical flighting 2315 on the cylindrical wallsof height h, and pitch p. The container 2300 in this example has apermanently attached base 2320 with a smaller opening 2325 of diameterd, in the center that is formed within a channel structure 2330 and thatis co-axial with the chamber 2310. The channel structure 2330 forms aco-axial spout feature. The base 2320 has a material-guiding structurein the form of an internal Archimedes screw 2335, or spiral feature,that is approximately the internal diameter of the chamber 2310 at thebottom of the base 2320 and that transitions to approximately thediameter of the central opening 2325 at the top of the base 2320, whereit forms part of a bottom of the channel structure 2330. Other examplesof this screw are shown in FIGS. 12A to 12E. The channel structure 2330and the spiral feature of the Archimedes screw 2335 have an axial holeof diameter d. D may be in a range of between 150 and 250 mm for athree-dimensional printing example, and L may be in a range of between400 and 600 mm. The diameter d may be in a range of 45 to 65 mm in thesame example.

The container of FIG. 23 also comprises a material-conveying member 2340in the form of an auger valve or helix screw of diameter d and length v.The length v may be in a range of 100 to 150 mm in an example. Thespiral auger feature of the material-conveying member 2340 matches thespiral feature of the Archimedes screw 2335. Further, in the presentexample, the spiral auger feature of the material-conveying member 2340mates with and completes the Archimedes screw when it is installed inthe opening 2325 to a depth that still allows the material-conveyingmember 2340 to protrude a distance o, representing the open position.The distance o may be in a range of 20 to 40 mm for a three-dimensionalprinting example. The material-conveying member 2340 further comprises avalve structure 2345 at its end. An O-ring 2350 for the valve structureis shown in the Figure. When the material-conveying member 2340 isinstalled to its full depth, the valve structure 2345 forms a seal forthe opening 2325. This represents a closed position of thematerial-conveying member 2340. The material-conveying member 2340 maybe keyed to the base 2320, e.g. to prevent relative rotation asdescribed above. The material-conveying member 2340 may compriseintegral spring ramps and stops, so that once installed it can then onlymove between closed and open positions and cannot rotate with respect tothe chamber 2310. The material-conveying member 2340 has a washer 2355and screw 2360 at the end of the member. These may function as theengagement member 918 described with reference to FIGS. 9D and 9E.Lastly a cap 2365 may be screwed onto the channel structure 2330 to sealthe container 2300, e.g. as per cap 951 shown in FIGS. 9F and 9G. Thecap 2365 may be tamper evident.

During operation, the container 2300 may be filled with fresh printingmaterial, e.g. at a site of filling and/or manufacture, and thematerial-conveying member 2340 installed. In this example, the keyingand other features limit future member movements to a predefined rangeof axial displacement.

Examples of containers as described herein enable powdered material tobe delivered with expected, original properties and flow behaviors. Forexample, by tumbling at various rotational speeds, powdered material inthe container can be mixed under several types of motion regimes,including slumping, rolling, cascading and cataracting. These motionregimes re-aerate and re-mix the powder, reversing the effects ofconsolidation, compaction and segregation.

The example containers described herein may be used for a wide range ofprinting materials. For example, they may be used for a wide variety ofpowder types, where each powder type may have different cohesiveproperties, compaction behaviors and segregation. In certain examples, acontainer may further comprise electronic circuitry adapted toelectronically communicate a printing material type installed within thecontainer to a printing system. For example, a wired or wirelessinterface may transmit data loaded into a chip in the container. Thecontainer may then be monitored when installed within a printing systemand rotated according to a specific routine for the printing materialtype therein (e.g. a set speed and direction that has been successful atrefreshing the properties of the specific material type in the past).Once the material properties are refreshed, the container may have amaterial-conveying member opened by the printing system, e.g. as shownin FIGS. 9D and 9E, and then be rotated at a speed and direction todispense the printing material. As long as the rotational speed is lowera speed known to cause centrifuging, and the internal supply surface isnot rough or electrostatically charged, a significant portion of theprinting material will be dispensed.

As well as providing benefits for printing material supply, the examplecontainers described herein also allow fresh or excess printing materialto be efficiently loaded back into the container. Fresh material may beloaded when switching between printing material types. By feeding powderto a material-conveying member while rotating the container in reverseat relatively low rotational speeds, the printing material may be movedinto the container by the material-conveying member and then furtherinto the container chamber by the internal raised portions (e.g. theribs or flighting).

To increase a rate and efficiency of fill, the rotational speed may beincreased such that a printing material within the container enters acentrifuging motion regime, where the centrifugal forces on the materialparticles become larger than gravitational forces. In this case, theprinting material may form a tube coating the cylindrical chamber innerwalls. Printing material that is introduced by the material-conveyingmember then moves into the chamber near the rotational axis (wherecentrifugal forces are smallest) and, once inside, moves towards theouter walls and flows axially to maintain a cylinder shape. In thiscase, the printing material layer thickens as more material isintroduced, and the cylinder of air in the center of the chamber getssmaller and smaller. A rotational speed, in revolutions per minute, toachieve centrifuging may be determined as a speed equal to 42.3 dividedby the square root of the inner diameter. If a goal is to remove as muchexcess powder from the printer as possible, the rotational speed can beincreased to cause compaction of the material layer and thus increasethe capacity of the removal. If a goal is to remove used printingmaterial for reuse at a later time, or fresh material for a materialchange, the container can be filled to a normal level, leaving some airvolume in the inner chamber, so the printing material can be refreshedby later tumbling. In either case, the material-conveying member may beclosed (e.g. by reversing the sequence shown in FIGS. 9D and 9E) by theprinting system and released. A user may then be notified by theprinting system that they can remove the full container.

Certain examples described herein provide more efficient use of spacethan comparative gravity feed hopper supplies, e.g. where the feedhopper is fed by pouring printing material into the hopper. Gravity feedhoppers have steep angles to ensure a flow of printing material. In thepresent examples, printing material may be fed by rotating thecontainer. As the containers may be mounted horizontally, they avoidtall vertical feed systems and hoppers. Certain examples describedherein also reduce an effect of compaction by rotating the container,which avoids manual shaking, tipping or tumbling. The containersdescribed in examples herein further provide a simple solution thatreduces or avoids the wear and higher complexity of internal augersand/or mixers within the printing system. They also reduce and/or avoidthe separation of printing material that may occur with comparativevacuum systems.

Certain examples described herein present a container for a printingmaterial, e.g. in powder form, that may be installed horizontally,rotated to re-mix, re-aerate and refresh the flow properties of thematerial, and that may deliver the material to a printing system at acontrolled rate. In addition, the same container, when coupled to amaterial supply may be arranged to accept printing material from theprinting system when requested, and may be filled to at least 95% of itsinternal volume while remaining in the horizontal orientation. Incertain described examples, the container has a material-conveyingmember, e.g. in the form of a central auger valve, that opens to moveprinting material in or out of the container depending on the rotationdirection. In certain described examples, a material-guiding structure,e.g. in the form of an Archimedes screw, may be used to move printingmaterial between edges of the container and the axial material-conveyingmember. In further examples, helical raised portions, e.g. in the formof ribs or a flighting, on the cylindrical walls may be used to moveprinting material along the direction of the container axis. Thesefeatures may be supplied individually or in a combination of two or morecomponents, wherein in the latter case they may interact to provide asynergistic effect. The container may be scaled to a variety of sizes,while still retaining the benefits discussed herein.

The preceding description has been presented to illustrate and describecertain examples. Different sets of examples have been described; thesemay be applied individually or in combination for a synergetic effect.This description is not intended to be exhaustive or to limit theseprinciples to any precise form disclosed. Many modifications andvariations are possible in light of the above teaching. It is to beunderstood that any feature described in relation to any one example maybe used alone, or in combination with other features described, and mayalso be used in combination with any features of any other of theexamples, or any combination of any other of the examples.

What is claimed is:
 1. A base for a printing material container,comprising: a channel structure defining an opening of the base, an axisof the channel structure defining an axial direction: and amaterial-guiding structure, formed around the opening, having a helicallower surface that extends from the channel structure in the axialdirection, wherein an upper surface of the material-guiding structure isformed by a lower surface of the base and the helical lower surfacemeets the lower surface of the base at a curved side wall that extendsradially from the channel structure to an annular portion of the base.2. The base of claim 1, wherein the material-guiding structure isconfigured to convey printing material to a material-conveying memberwhen the base is rotated about the axis of the channel structure, thematerial-conveying member being configured to convey printing materialthrough the channel structure.
 3. The base of claim 2, wherein thematerial-conveying member is a multi-helix screw at least partiallydisposed within the channel structure.
 4. The base of claim 1, whereinthe helical lower surface forms a curve of narrowing radius.
 5. The baseof claim 4, wherein the helical lower surface has a maximum radius and aminimum radius, the maximum radius being between two and four times theminimum radius.
 6. The base of claim 4, wherein the narrowing radius isa continuously narrowing radius.
 7. The base of claim 1, wherein thematerial-guiding structure has a predefined volume.
 8. The base of claim1, wherein the material-guiding structure is an integral molded elementof the base.
 9. A method of conveying a printing material between astorage container and a printing system, comprising: providing a storagecontainer with an integral scoop, the integral scoop being arrangedaround a channel structure of the storage container, the channelstructure extending along an axis of the storage container, the integralscoop having a helical floor that surrounds an opening of the channelstructure, a meeting point between the helical floor and a surface ofthe storage container forming a curve of narrowing radius; and rotatingthe storage container about the axis so as to rotate the integral scoopto convey the printing material between an interior of the container andthe channel structure.
 10. The method of claim 9, wherein the rotationof the storage container causes the integral scoop to operate as anArchimedes screw.
 11. The method of claim 9, wherein performing acomplete rotation of the storage container conveys at least one discretedose of printing material.
 12. The method of claim 9, wherein theprinting material comprises a powder.
 13. The method of claim 9, whereinthe printing material comprises a build material for a three-dimensionalprinting system.
 14. The method of claim 11, comprising conveying theprinting material to a material-conveying member at least partiallydisposed within the channel structure.
 15. A container for a printingsystem, comprising: a chamber for storing a printing material; amaterial-conveying member; and a base comprising: an opening to receivethe material-conveying member, a shared axis of the opening and thematerial-conveying member defining an axial direction of the container;and a material-guiding structure formed around the opening having ahelical lower surface that extends from the base into the chamber in theaxial direction, wherein at least a portion of an outer side wall of thematerial-guiding structure abuts an inner side wall of the chamber,wherein an upper surface of the material-guiding structure is formed bya lower surface of the base, and wherein the helical lower surface meetsthe lower surface of the base at a curved side wall that extendsradially from the channel structure to the outer side wall.